From 522fcba637d0bc096f4a1146d121eec240bb333c Mon Sep 17 00:00:00 2001 From: Leith14 Date: Fri, 13 Dec 2019 14:31:16 +0800 Subject: [PATCH 01/31] 576-Week 08 --- .idea/algorithm004-01.iml | 9 +++++ .idea/codeStyles/codeStyleConfig.xml | 5 +++ .idea/misc.xml | 4 ++ .idea/modules.xml | 8 ++++ .idea/vcs.xml | 6 +++ Week 07/id_576/MergeSort.java | 4 ++ Week 08/id_576/LeetCode_10_576.java | 4 ++ Week 08/id_576/LeetCode_1143_576.java | 28 ++++++++++++++ Week 08/id_576/LeetCode_115_576.java | 4 ++ Week 08/id_576/LeetCode_125_576.java | 4 ++ Week 08/id_576/LeetCode_14_576.java | 33 ++++++++++++++++ Week 08/id_576/LeetCode_151_576.java | 4 ++ Week 08/id_576/LeetCode_300_576.java | 4 ++ Week 08/id_576/LeetCode_344_576.java | 4 ++ Week 08/id_576/LeetCode_387_576.java | 35 +++++++++++++++++ Week 08/id_576/LeetCode_438_576.java | 4 ++ Week 08/id_576/LeetCode_541_576.java | 4 ++ Week 08/id_576/LeetCode_5_576.java | 56 +++++++++++++++++++++++++++ Week 08/id_576/LeetCode_680_576.java | 4 ++ Week 08/id_576/LeetCode_72_576.java | 36 +++++++++++++++++ Week 08/id_576/LeetCode_746_576.java | 4 ++ Week 08/id_576/LeetCode_8_576.java | 4 ++ 22 files changed, 268 insertions(+) create mode 100644 .idea/algorithm004-01.iml create mode 100644 .idea/codeStyles/codeStyleConfig.xml create mode 100644 .idea/misc.xml create mode 100644 .idea/modules.xml create mode 100644 .idea/vcs.xml create mode 100644 Week 07/id_576/MergeSort.java create mode 100644 Week 08/id_576/LeetCode_10_576.java create mode 100644 Week 08/id_576/LeetCode_1143_576.java create mode 100644 Week 08/id_576/LeetCode_115_576.java create mode 100644 Week 08/id_576/LeetCode_125_576.java create mode 100644 Week 08/id_576/LeetCode_14_576.java create mode 100644 Week 08/id_576/LeetCode_151_576.java create mode 100644 Week 08/id_576/LeetCode_300_576.java create mode 100644 Week 08/id_576/LeetCode_344_576.java create mode 100644 Week 08/id_576/LeetCode_387_576.java create mode 100644 Week 08/id_576/LeetCode_438_576.java create mode 100644 Week 08/id_576/LeetCode_541_576.java create mode 100644 Week 08/id_576/LeetCode_5_576.java create mode 100644 Week 08/id_576/LeetCode_680_576.java create mode 100644 Week 08/id_576/LeetCode_72_576.java create mode 100644 Week 08/id_576/LeetCode_746_576.java create mode 100644 Week 08/id_576/LeetCode_8_576.java diff --git a/.idea/algorithm004-01.iml b/.idea/algorithm004-01.iml new file mode 100644 index 000000000..d6ebd4805 --- /dev/null +++ b/.idea/algorithm004-01.iml @@ -0,0 +1,9 @@ + + + + + + + + + \ No newline at end of file diff --git a/.idea/codeStyles/codeStyleConfig.xml b/.idea/codeStyles/codeStyleConfig.xml new file mode 100644 index 000000000..a55e7a179 --- /dev/null +++ b/.idea/codeStyles/codeStyleConfig.xml @@ -0,0 +1,5 @@ + + + + \ No newline at end of file diff --git a/.idea/misc.xml b/.idea/misc.xml new file mode 100644 index 000000000..53c721fe9 --- /dev/null +++ b/.idea/misc.xml @@ -0,0 +1,4 @@ + + + + \ No newline at end of file diff --git a/.idea/modules.xml b/.idea/modules.xml new file mode 100644 index 000000000..156db0a63 --- /dev/null +++ b/.idea/modules.xml @@ -0,0 +1,8 @@ + + + + + + + + \ No newline at end of file diff --git a/.idea/vcs.xml b/.idea/vcs.xml new file mode 100644 index 000000000..35eb1ddfb --- /dev/null +++ b/.idea/vcs.xml @@ -0,0 +1,6 @@ + + + + + + \ No newline at end of file diff --git a/Week 07/id_576/MergeSort.java b/Week 07/id_576/MergeSort.java new file mode 100644 index 000000000..e46877d88 --- /dev/null +++ b/Week 07/id_576/MergeSort.java @@ -0,0 +1,4 @@ +package id_576; + +public class MergeSort { +} diff --git a/Week 08/id_576/LeetCode_10_576.java b/Week 08/id_576/LeetCode_10_576.java new file mode 100644 index 000000000..1374c0140 --- /dev/null +++ b/Week 08/id_576/LeetCode_10_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_10_576 { +} diff --git a/Week 08/id_576/LeetCode_1143_576.java b/Week 08/id_576/LeetCode_1143_576.java new file mode 100644 index 000000000..f4f3842ae --- /dev/null +++ b/Week 08/id_576/LeetCode_1143_576.java @@ -0,0 +1,28 @@ +package id_576; + +public class LeetCode_1143_576 { + + public int longestCommonSubsequence(String text1, String text2) { + int m = text1.length(); + int n = text2.length(); + int[][] dp = new int[m + 1][n + 1]; + for (int i = 1; i < m + 1; i++) { + for (int j = 1; j < n + 1; j++) { + if (text1.charAt(i) == text2.charAt(j)) { + //需要注意数组越界的问题 + dp[i][j] = dp[i - 1][j - 1] + 1; + } + dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]); + } + } + return dp[m][n]; + } + + /** + * 如果是最长公共子串，dp方程将改为 + * dp[i][j] = dp[i-1][j-1] + 1(if s1[i-1] == s2[j-1]) + * else dp[i][j] = 0 + * + * return Max(dp[i][j]) + */ +} diff --git a/Week 08/id_576/LeetCode_115_576.java b/Week 08/id_576/LeetCode_115_576.java new file mode 100644 index 000000000..5b7750a2c --- /dev/null +++ b/Week 08/id_576/LeetCode_115_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_115_576 { +} diff --git a/Week 08/id_576/LeetCode_125_576.java b/Week 08/id_576/LeetCode_125_576.java new file mode 100644 index 000000000..16afd5c84 --- /dev/null +++ b/Week 08/id_576/LeetCode_125_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_125_576 { +} diff --git a/Week 08/id_576/LeetCode_14_576.java b/Week 08/id_576/LeetCode_14_576.java new file mode 100644 index 000000000..05938dd50 --- /dev/null +++ b/Week 08/id_576/LeetCode_14_576.java @@ -0,0 +1,33 @@ +package id_576; + +public class LeetCode_14_576 { + + /** + * 1.brute + * 2. approach 1 + * 3. Trie + * @param strs + * @return + */ + public String longestCommonPrefix1(String[] strs) { + if (strs == null || strs.length == 0) return ""; + for (int i = 0; i < strs[0].length(); i++) { + char c = strs[0].charAt(i); + for (int j = 1; j < strs.length ; j++) { + if (i == strs[j].length() || strs[j].charAt(i) != c) + return strs[0].substring(0, i); + } + } + return strs[0]; + } + + public String longestCommonPrefix2(String[] strs) { + + return null; + } + + public String longestCommonPrefix3(String[] strs) { + + return null; + } +} diff --git a/Week 08/id_576/LeetCode_151_576.java b/Week 08/id_576/LeetCode_151_576.java new file mode 100644 index 000000000..0dd6f0712 --- /dev/null +++ b/Week 08/id_576/LeetCode_151_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_151_576 { +} diff --git a/Week 08/id_576/LeetCode_300_576.java b/Week 08/id_576/LeetCode_300_576.java new file mode 100644 index 000000000..95a46877b --- /dev/null +++ b/Week 08/id_576/LeetCode_300_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_300_576 { +} diff --git a/Week 08/id_576/LeetCode_344_576.java b/Week 08/id_576/LeetCode_344_576.java new file mode 100644 index 000000000..d0655c870 --- /dev/null +++ b/Week 08/id_576/LeetCode_344_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_344_576 { +} diff --git a/Week 08/id_576/LeetCode_387_576.java b/Week 08/id_576/LeetCode_387_576.java new file mode 100644 index 000000000..afbf5433e --- /dev/null +++ b/Week 08/id_576/LeetCode_387_576.java @@ -0,0 +1,35 @@ +package id_576; + +import java.util.HashMap; +import java.util.Map; + + +public class LeetCode_387_576 { + + // Approach 1: Map(hashmap(O(1)), treemap(O(logN))) and for loop, O(n)/O(nlogn) + public int firstUniqChar1(String s) { + Map res = new HashMap(); + for (int i = 0; i < s.length(); i++) { + res.put(s.charAt(i), res.getOrDefault(s.charAt(i), 0) + 1); + } + + for (int i = 0; i < s.length(); i++) { + if (res.get(s.charAt(i)) == 1) { + return i; + } + } + return -1; + } + + // Approach 2: brute-force, O(n^2),i 枚举所有字符，j枚举i后面的所有字符 + public int firstUniqChar2(String s) { + + return 0; + } + + // Approach 3: hash table + public int firstUniqChar3(String s) { + + return 0; + } +} diff --git a/Week 08/id_576/LeetCode_438_576.java b/Week 08/id_576/LeetCode_438_576.java new file mode 100644 index 000000000..c61a30ca2 --- /dev/null +++ b/Week 08/id_576/LeetCode_438_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_438_576 { +} diff --git a/Week 08/id_576/LeetCode_541_576.java b/Week 08/id_576/LeetCode_541_576.java new file mode 100644 index 000000000..a251448b8 --- /dev/null +++ b/Week 08/id_576/LeetCode_541_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_541_576 { +} diff --git a/Week 08/id_576/LeetCode_5_576.java b/Week 08/id_576/LeetCode_5_576.java new file mode 100644 index 000000000..a8cc69d1f --- /dev/null +++ b/Week 08/id_576/LeetCode_5_576.java @@ -0,0 +1,56 @@ +package id_576; + +public class LeetCode_5_576 { + + /** + * 1. brute 嵌套循环，枚举 i， j（起点和终点），判断子串是否是回文串, O(n^3) + * 2. 枚举中心，向两边扩张O(n^2) + * 3. DP + * @param s + * @return + */ + public String longestPalindrome1(String s) { + int n = s.length(); + String res = ""; + boolean[][] dp = new boolean[n][n]; + for (int i = n - 1; i >= 0; i--) { + for (int j = i; j < n; j++) { + dp[i][j] = s.charAt(i) == s.charAt(j) && + (j - i < 2 || dp[i + 1][j - 1]); + + if (dp[i][j] && j - i + 1 > res.length()) { + res = s.substring(i, j + 1); + } + } + } + return res; + } + + private int lo, maxlen; + public String longestPalindrome2(String s) { + int len = s.length(); + if (len < 2) { + return s; + } + + for (int i = 0; i < len - 1; i++) { + extendPalindrome(s, i, i); // odd length + extendPalindrome(s, i, i + 1); // even length + } + + return s.substring(lo, lo + maxlen); + } + + private void extendPalindrome(String s, int j, int k) { + while (j >= 0 && k < s.length() && s.charAt(j) == s.charAt(k)) { + j--; k++; + } + + if (maxlen < k - j - 1) { + lo = j + 1; + maxlen = k - j - 1; + } + } + + +} diff --git a/Week 08/id_576/LeetCode_680_576.java b/Week 08/id_576/LeetCode_680_576.java new file mode 100644 index 000000000..3166915a8 --- /dev/null +++ b/Week 08/id_576/LeetCode_680_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_680_576 { +} diff --git a/Week 08/id_576/LeetCode_72_576.java b/Week 08/id_576/LeetCode_72_576.java new file mode 100644 index 000000000..8669660e6 --- /dev/null +++ b/Week 08/id_576/LeetCode_72_576.java @@ -0,0 +1,36 @@ +package id_576; + +public class LeetCode_72_576 { + + // Approach1: BFS, twe-ended BFS + public int minDistance1(String word1, String word2) { + + return 0; + } + + // Approach2: DP + /** + * dp[i] 如何定义？ + * dp[i][j] // word1.substr(0,i) 与 + * word2.substr(0,j) 之间的编辑距离 + * 感觉跟uniquepath那道题差不多 + */ + + public int minDistance2(String word1, String word2) { + int n1 = word1.length(); + int n2 = word2.length(); + int[][] dp = new int[n1 + 1][n2 + 1]; + // first row + for (int j = 1; j <= n2 ; j++) dp[0][j] = dp[0][j - 1] + 1; + // first col + for (int i = 1; i <= n1 ; i++) dp[i][0] = dp[i - 1][0] + 1; + + for (int i = 1; i <= n1 ; i++) { + for (int j = 1; j <= n2 ; j++) { + if (word1.charAt(i - 1) == word2.charAt(j - 1)) dp[i][j] = dp[i - 1][j - 1]; + else dp[i][j] = Math.min(Math.min(dp[i - 1][j - 1], dp[i - 1][j]), dp[i][j - 1]) + 1; + } + } + return dp[n1][n2]; + } +} diff --git a/Week 08/id_576/LeetCode_746_576.java b/Week 08/id_576/LeetCode_746_576.java new file mode 100644 index 000000000..2cc960206 --- /dev/null +++ b/Week 08/id_576/LeetCode_746_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_746_576 { +} diff --git a/Week 08/id_576/LeetCode_8_576.java b/Week 08/id_576/LeetCode_8_576.java new file mode 100644 index 000000000..32f94ec91 --- /dev/null +++ b/Week 08/id_576/LeetCode_8_576.java @@ -0,0 +1,4 @@ +package id_576; + +public class LeetCode_8_576 { +} From 85e2726b13254984f058c05880ab6f5d01b99f32 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:43:50 +0800 Subject: [PATCH 02/31] Delete LeetCode_10_576.java --- Week 08/id_576/LeetCode_10_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_10_576.java diff --git a/Week 08/id_576/LeetCode_10_576.java b/Week 08/id_576/LeetCode_10_576.java deleted file mode 100644 index 1374c0140..000000000 --- a/Week 08/id_576/LeetCode_10_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_10_576 { -} From 11d8ce6aa231cf6398129521dd1c047784b6ca04 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:44:21 +0800 Subject: [PATCH 03/31] Delete LeetCode_8_576.java --- Week 08/id_576/LeetCode_8_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_8_576.java diff --git a/Week 08/id_576/LeetCode_8_576.java b/Week 08/id_576/LeetCode_8_576.java deleted file mode 100644 index 32f94ec91..000000000 --- a/Week 08/id_576/LeetCode_8_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_8_576 { -} From 5f7069d6f5e4e8caec991203f4f78017ae962213 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:44:33 +0800 Subject: [PATCH 04/31] Delete LeetCode_115_576.java --- Week 08/id_576/LeetCode_115_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_115_576.java diff --git a/Week 08/id_576/LeetCode_115_576.java b/Week 08/id_576/LeetCode_115_576.java deleted file mode 100644 index 5b7750a2c..000000000 --- a/Week 08/id_576/LeetCode_115_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_115_576 { -} From 973c5ee96e77005978c3ad4eff2293d9128fdfd6 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:44:53 +0800 Subject: [PATCH 05/31] Delete LeetCode_125_576.java --- Week 08/id_576/LeetCode_125_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_125_576.java diff --git a/Week 08/id_576/LeetCode_125_576.java b/Week 08/id_576/LeetCode_125_576.java deleted file mode 100644 index 16afd5c84..000000000 --- a/Week 08/id_576/LeetCode_125_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_125_576 { -} From 9fe2b9a9b1afc74884b931ec542e46887393ffa4 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:47:47 +0800 Subject: [PATCH 06/31] Delete LeetCode_151_576.java --- Week 08/id_576/LeetCode_151_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_151_576.java diff --git a/Week 08/id_576/LeetCode_151_576.java b/Week 08/id_576/LeetCode_151_576.java deleted file mode 100644 index 0dd6f0712..000000000 --- a/Week 08/id_576/LeetCode_151_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_151_576 { -} From 9b3382783050c09b188902c5e01596be04c424e2 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:48:13 +0800 Subject: [PATCH 07/31] Delete LeetCode_300_576.java --- Week 08/id_576/LeetCode_300_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_300_576.java diff --git a/Week 08/id_576/LeetCode_300_576.java b/Week 08/id_576/LeetCode_300_576.java deleted file mode 100644 index 95a46877b..000000000 --- a/Week 08/id_576/LeetCode_300_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_300_576 { -} From 692b1e39a04376aec6e7d67fcc1351349d4ab598 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:48:25 +0800 Subject: [PATCH 08/31] Delete LeetCode_344_576.java --- Week 08/id_576/LeetCode_344_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_344_576.java diff --git a/Week 08/id_576/LeetCode_344_576.java b/Week 08/id_576/LeetCode_344_576.java deleted file mode 100644 index d0655c870..000000000 --- a/Week 08/id_576/LeetCode_344_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_344_576 { -} From fe3fc9b47f7f2ee2c79b01595d9171226fe06671 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:48:59 +0800 Subject: [PATCH 09/31] Delete LeetCode_438_576.java --- Week 08/id_576/LeetCode_438_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_438_576.java diff --git a/Week 08/id_576/LeetCode_438_576.java b/Week 08/id_576/LeetCode_438_576.java deleted file mode 100644 index c61a30ca2..000000000 --- a/Week 08/id_576/LeetCode_438_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_438_576 { -} From afa317a5ee992df7f1fda970a933e51228e51502 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:49:21 +0800 Subject: [PATCH 10/31] Delete LeetCode_541_576.java --- Week 08/id_576/LeetCode_541_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_541_576.java diff --git a/Week 08/id_576/LeetCode_541_576.java b/Week 08/id_576/LeetCode_541_576.java deleted file mode 100644 index a251448b8..000000000 --- a/Week 08/id_576/LeetCode_541_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_541_576 { -} From d0e94aab859a467d88f6cf798d2edca9019ebfe8 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:49:42 +0800 Subject: [PATCH 11/31] Delete LeetCode_680_576.java --- Week 08/id_576/LeetCode_680_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_680_576.java diff --git a/Week 08/id_576/LeetCode_680_576.java b/Week 08/id_576/LeetCode_680_576.java deleted file mode 100644 index 3166915a8..000000000 --- a/Week 08/id_576/LeetCode_680_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_680_576 { -} From bf1e1419a7be933be2ab3e6202240b7b58c99f2f Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:50:06 +0800 Subject: [PATCH 12/31] Delete LeetCode_746_576.java --- Week 08/id_576/LeetCode_746_576.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 08/id_576/LeetCode_746_576.java diff --git a/Week 08/id_576/LeetCode_746_576.java b/Week 08/id_576/LeetCode_746_576.java deleted file mode 100644 index 2cc960206..000000000 --- a/Week 08/id_576/LeetCode_746_576.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class LeetCode_746_576 { -} From 1ea743aa5ad0d62304a8b70234d841700fcc159f Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:55:24 +0800 Subject: [PATCH 13/31] Delete codeStyleConfig.xml --- .idea/codeStyles/codeStyleConfig.xml | 5 ----- 1 file changed, 5 deletions(-) delete mode 100644 .idea/codeStyles/codeStyleConfig.xml diff --git a/.idea/codeStyles/codeStyleConfig.xml b/.idea/codeStyles/codeStyleConfig.xml deleted file mode 100644 index a55e7a179..000000000 --- a/.idea/codeStyles/codeStyleConfig.xml +++ /dev/null @@ -1,5 +0,0 @@ - - - - \ No newline at end of file From abb8005e552ce4d08fe3fc95488fc5873c22e998 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:55:37 +0800 Subject: [PATCH 14/31] Delete algorithm004-01.iml --- .idea/algorithm004-01.iml | 9 --------- 1 file changed, 9 deletions(-) delete mode 100644 .idea/algorithm004-01.iml diff --git a/.idea/algorithm004-01.iml b/.idea/algorithm004-01.iml deleted file mode 100644 index d6ebd4805..000000000 --- a/.idea/algorithm004-01.iml +++ /dev/null @@ -1,9 +0,0 @@ - - - - - - - - - \ No newline at end of file From e115097d210fe5678b8d33a32e434b7646e7f57f Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:55:47 +0800 Subject: [PATCH 15/31] Delete misc.xml --- .idea/misc.xml | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 .idea/misc.xml diff --git a/.idea/misc.xml b/.idea/misc.xml deleted file mode 100644 index 53c721fe9..000000000 --- a/.idea/misc.xml +++ /dev/null @@ -1,4 +0,0 @@ - - - - \ No newline at end of file From 65eedeff0f8cf3cbba30a98dec0582d1eaec618b Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:55:56 +0800 Subject: [PATCH 16/31] Delete modules.xml --- .idea/modules.xml | 8 -------- 1 file changed, 8 deletions(-) delete mode 100644 .idea/modules.xml diff --git a/.idea/modules.xml b/.idea/modules.xml deleted file mode 100644 index 156db0a63..000000000 --- a/.idea/modules.xml +++ /dev/null @@ -1,8 +0,0 @@ - - - - - - - - \ No newline at end of file From b776f08389fdf0850f992c35b70053b5bd591027 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:56:07 +0800 Subject: [PATCH 17/31] Delete vcs.xml --- .idea/vcs.xml | 6 ------ 1 file changed, 6 deletions(-) delete mode 100644 .idea/vcs.xml diff --git a/.idea/vcs.xml b/.idea/vcs.xml deleted file mode 100644 index 35eb1ddfb..000000000 --- a/.idea/vcs.xml +++ /dev/null @@ -1,6 +0,0 @@ - - - - - - \ No newline at end of file From 0f3aa958b2b61f18abad2ebe1010a97df5411b2e Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 14:56:38 +0800 Subject: [PATCH 18/31] Delete MergeSort.java --- Week 07/id_576/MergeSort.java | 4 ---- 1 file changed, 4 deletions(-) delete mode 100644 Week 07/id_576/MergeSort.java diff --git a/Week 07/id_576/MergeSort.java b/Week 07/id_576/MergeSort.java deleted file mode 100644 index e46877d88..000000000 --- a/Week 07/id_576/MergeSort.java +++ /dev/null @@ -1,4 +0,0 @@ -package id_576; - -public class MergeSort { -} From 83f803fd92d43d1c9bff53dfd183d4d2615bc8c0 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 15:38:59 +0800 Subject: [PATCH 19/31] Update LeetCode_212_576.java --- Week 06/id_576/LeetCode_212_576.java | 86 ++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) diff --git a/Week 06/id_576/LeetCode_212_576.java b/Week 06/id_576/LeetCode_212_576.java index e69de29bb..5f4f028e3 100644 --- a/Week 06/id_576/LeetCode_212_576.java +++ b/Week 06/id_576/LeetCode_212_576.java @@ -0,0 +1,86 @@ +package id_576; + +import java.util.HashSet; +import java.util.LinkedList; +import java.util.List; +import java.util.Set; + +public class LeetCode_212_576 { + public List findWords(char[][] board, String[] words) { + //构建字典树 + wordTrie myTrie=new wordTrie(); + trieNode root=myTrie.root; + for(String s:words) + myTrie.insert(s); + + //使用set防止重复 + Set result =new HashSet<>(); + int m=board.length; + int n=board[0].length; + boolean [][]visited=new boolean[m][n]; + //遍历整个二维数组 + for(int i=0;i(result); + } + private void find(char [] [] board, boolean [][]visited,int i,int j,int m,int n,Set result,trieNode cur){ + //边界以及是否已经访问判断 + if(i<0||i>=m||j<0||j>=n||visited[i][j]) + return; + cur=cur.child[board[i][j]-'a']; + visited[i][j]=true; + if(cur==null) + { + //如果单词不匹配，回退 + visited[i][j]=false; + return; + } + //找到单词加入 + if(cur.isLeaf) + { + result.add(cur.val); + //找到单词后不能回退，因为可能是“ad” “addd”这样的单词得继续回溯 +// visited[i][j]=false; +// return; + } + find(board,visited,i+1,j,m,n,result,cur); + find(board,visited,i,j+1,m,n,result,cur); + find(board,visited,i,j-1,m,n,result,cur); + find(board,visited,i-1,j,m,n,result,cur); + //最后要回退，因为下一个起点可能会用到上一个起点的字符 + visited[i][j]=false; + } + + +} + +//字典树 +class wordTrie{ + public trieNode root=new trieNode(); + public void insert(String s){ + trieNode cur=root; + for(char c:s.toCharArray()){ + if(cur.child[c-'a']==null){ + cur.child [c-'a'] = new trieNode(); + cur=cur.child[c-'a']; + }else + cur=cur.child [c-'a']; + } + cur.isLeaf=true; + cur.val=s; + } +} +//字典树结点 +class trieNode{ + public String val; + public trieNode[] child=new trieNode[26]; + public boolean isLeaf=false; + + trieNode(){ + + } +} From 08b6ed22be78f3a6e111eafff07b7957343afe9f Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Fri, 13 Dec 2019 15:39:29 +0800 Subject: [PATCH 20/31] Update LeetCode_547_576.java --- Week 06/id_576/LeetCode_547_576.java | 53 ++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/Week 06/id_576/LeetCode_547_576.java b/Week 06/id_576/LeetCode_547_576.java index e69de29bb..d6e3fe1b2 100644 --- a/Week 06/id_576/LeetCode_547_576.java +++ b/Week 06/id_576/LeetCode_547_576.java @@ -0,0 +1,53 @@ +package id_576; + +public class LeetCode_547_576 { + + class UnionFind { + private int count = 0; + private int[] parent, rank; + public UnionFind(int n) { + count = n; + parent = new int[n]; + rank = new int[n]; + for (int i = 0; i < n; i++) { + parent[i] = i; + } + } + + public int find(int p) { + while (p != parent[p]) { + parent[p] = parent[parent[p]]; + p = parent[p]; + } + return p; + } + public void union(int p, int q) { + int rootP = find(p); + int rootQ = find(q); + if (rootP == rootQ) return; + if (rank[rootQ] > rank[rootP]) { + parent[rootP] = rootQ; + } else { + parent[rootQ] = rootP; + if (rank[rootP] == rank[rootQ]) { + rank[rootP]++; + } + } + count--; + } + public int count() { + return count; + } + + } + public int findCircleNum(int[][] M) { + int n = M.length; + UnionFind uf = new UnionFind(n); + for (int i = 0; i < n - 1 ; i++) { + for (int j = i + 1; j < n; j++) { + if (M[i][j] == 1) uf.union(i, j); + } + } + return uf.count(); + } +} From 73d03cca78d921d90f06856dd08cbf152b8e0b11 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 15:00:04 +0800 Subject: [PATCH 21/31] Create LeetCode_144_576.java --- Week 02/id_576/LeetCode_144_576.java | 37 ++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 Week 02/id_576/LeetCode_144_576.java diff --git a/Week 02/id_576/LeetCode_144_576.java b/Week 02/id_576/LeetCode_144_576.java new file mode 100644 index 000000000..aa47b742e --- /dev/null +++ b/Week 02/id_576/LeetCode_144_576.java @@ -0,0 +1,37 @@ +package id_576; + +import java.util.HashMap; +import java.util.Map; + +public class LeetCode_1_576 { + + // Approach 1: hash table + public int[] twoSum1(int[] nums, int target) { + int[] res = new int[2]; + Map map = new HashMap<>(); + for (int i = 0; i < nums.length; ++i) { + if (map.containsKey(target - nums[i])) { + res[1] = i; + res[0] = map.get(target - nums[i]); + return res; + } + map.put(nums[i], i); + } + return res; + } + + // Approach 2: brute force, O(n^2) + public int[] twoSum2(int[] nums, int target) { + int[] res = new int[2]; + for (int i = 0; i < nums.length - 1; i++) { + for (int j = i + 1; j < nums.length; j++) { + if (nums[i] + nums[j] == target) { + res[0] = i; + res[1] = j; + return res; + } + } + } + return new int[0]; + } +} From 519e7e0261b16ed2a0ee5a05f6f5c553f4ca3efd Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 15:01:46 +0800 Subject: [PATCH 22/31] Delete LeetCode_144_576.java --- Week 02/id_576/LeetCode_144_576.java | 37 ---------------------------- 1 file changed, 37 deletions(-) delete mode 100644 Week 02/id_576/LeetCode_144_576.java diff --git a/Week 02/id_576/LeetCode_144_576.java b/Week 02/id_576/LeetCode_144_576.java deleted file mode 100644 index aa47b742e..000000000 --- a/Week 02/id_576/LeetCode_144_576.java +++ /dev/null @@ -1,37 +0,0 @@ -package id_576; - -import java.util.HashMap; -import java.util.Map; - -public class LeetCode_1_576 { - - // Approach 1: hash table - public int[] twoSum1(int[] nums, int target) { - int[] res = new int[2]; - Map map = new HashMap<>(); - for (int i = 0; i < nums.length; ++i) { - if (map.containsKey(target - nums[i])) { - res[1] = i; - res[0] = map.get(target - nums[i]); - return res; - } - map.put(nums[i], i); - } - return res; - } - - // Approach 2: brute force, O(n^2) - public int[] twoSum2(int[] nums, int target) { - int[] res = new int[2]; - for (int i = 0; i < nums.length - 1; i++) { - for (int j = i + 1; j < nums.length; j++) { - if (nums[i] + nums[j] == target) { - res[0] = i; - res[1] = j; - return res; - } - } - } - return new int[0]; - } -} From 2277f39b0a09aa659df4b5d693cd3809be52b0fd Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 15:02:16 +0800 Subject: [PATCH 23/31] Create LeetCode_1_576.java --- Week 02/id_576/LeetCode_1_576.java | 37 ++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 Week 02/id_576/LeetCode_1_576.java diff --git a/Week 02/id_576/LeetCode_1_576.java b/Week 02/id_576/LeetCode_1_576.java new file mode 100644 index 000000000..aa47b742e --- /dev/null +++ b/Week 02/id_576/LeetCode_1_576.java @@ -0,0 +1,37 @@ +package id_576; + +import java.util.HashMap; +import java.util.Map; + +public class LeetCode_1_576 { + + // Approach 1: hash table + public int[] twoSum1(int[] nums, int target) { + int[] res = new int[2]; + Map map = new HashMap<>(); + for (int i = 0; i < nums.length; ++i) { + if (map.containsKey(target - nums[i])) { + res[1] = i; + res[0] = map.get(target - nums[i]); + return res; + } + map.put(nums[i], i); + } + return res; + } + + // Approach 2: brute force, O(n^2) + public int[] twoSum2(int[] nums, int target) { + int[] res = new int[2]; + for (int i = 0; i < nums.length - 1; i++) { + for (int j = i + 1; j < nums.length; j++) { + if (nums[i] + nums[j] == target) { + res[0] = i; + res[1] = j; + return res; + } + } + } + return new int[0]; + } +} From bedd60fce5884177c65fff482d9b82db38058304 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 15:02:39 +0800 Subject: [PATCH 24/31] Create LeetCode_242_576.java --- Week 02/id_576/LeetCode_242_576.java | 33 ++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 Week 02/id_576/LeetCode_242_576.java diff --git a/Week 02/id_576/LeetCode_242_576.java b/Week 02/id_576/LeetCode_242_576.java new file mode 100644 index 000000000..e89bc708c --- /dev/null +++ b/Week 02/id_576/LeetCode_242_576.java @@ -0,0 +1,33 @@ +package id_576; + +import java.util.Arrays; + +public class LeetCode_242_576 { + + + public boolean isAnagram1(String s, String t) { + if (s.length() != t.length()) { + return false; + } + + char[] str1 = s.toCharArray(); + char[] str2 = t.toCharArray(); + Arrays.sort(str1); + Arrays.sort(str2); + return Arrays.equals(str1, str2); + } + + // Approach 2: hash、map，统计每个字符的频次 + public boolean isAnagram2(String s, String t) { + if (s.length() != t.length()) { + return false; + } + int[] counter = new int[26]; + for (int i = 0; i < s.length(); i++) { + counter[s.charAt(i) - 'a']++; + counter[t.charAt(i) - 'a']--; + } + for (int count:counter) if (count != 0) return false; + return true; + } +} From a55d6961bbca6652b7402222cdc351c3fc288722 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 15:03:00 +0800 Subject: [PATCH 25/31] Create LeetCode_49_576.java --- Week 02/id_576/LeetCode_49_576.java | 41 +++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 Week 02/id_576/LeetCode_49_576.java diff --git a/Week 02/id_576/LeetCode_49_576.java b/Week 02/id_576/LeetCode_49_576.java new file mode 100644 index 000000000..640522915 --- /dev/null +++ b/Week 02/id_576/LeetCode_49_576.java @@ -0,0 +1,41 @@ +package id_576; + +import java.util.*; + +public class LeetCode_49_576 { + + // Approach 1: sort, O(k * n * logN) + public List> groupAnagrams1(String[] strs) { + if (strs.length == 0) return new ArrayList<>(); + Map> ans = new HashMap<>(); + for (String s : strs) { + char[] ca = s.toCharArray(); + Arrays.sort(ca); + String key = String.valueOf(ca); + if (!ans.containsKey(key)) ans.put(key, new ArrayList<>()); + ans.get(key).add(s); + } + return new ArrayList<>(ans.values()); + } + + // Approach 2: counter, O(k * n * logN) + public List> groupAnagrams2(String[] strs) { + if (strs.length == 0) return new ArrayList<>(); + Map> ans = new HashMap<>(); + int[] count = new int[26]; + for (String s: strs) { + Arrays.fill(count, 0); + for (char c : s.toCharArray()) count[c - 'a']++; + + StringBuilder sb = new StringBuilder(""); + for (int i = 0; i < 26; i++) { + sb.append('#'); + sb.append(count[i]); + } + String key = sb.toString(); + if (!ans.containsKey(key)) ans.put(key, new ArrayList<>()); + ans.get(key).add(s); + } + return new ArrayList<>(ans.values()); + } +} From e8ccf6e6d7cbbb6d7c3e6263f0de000aa9a44a7d Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 22:37:47 +0800 Subject: [PATCH 26/31] Create LeetCode_94_576.java --- Week 02/id_576/LeetCode_94_576.java | 43 +++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 Week 02/id_576/LeetCode_94_576.java diff --git a/Week 02/id_576/LeetCode_94_576.java b/Week 02/id_576/LeetCode_94_576.java new file mode 100644 index 000000000..38dc54b9c --- /dev/null +++ b/Week 02/id_576/LeetCode_94_576.java @@ -0,0 +1,43 @@ +package id_576; + +import java.util.ArrayList; +import java.util.List; +import java.util.Stack; + +public class LeetCode_94_576 { + + + // Approach 1: recursion, O(n) + public List inorderTraversal1(TreeNode root) { + List res = new ArrayList<>(); + helper(root, res); + return res; + } + + private void helper(TreeNode root, List res) { + if (root != null) { + if (root.left != null) helper(root.left, res); + res.add(root.val); + if (root.right != null) helper(root.right, res); + } + } + + // Approach 2: create a stack with manual, O(n) + public List inorderTraversal2(TreeNode root) { + List res = new ArrayList<>(); + Stack stack = new Stack<>(); + TreeNode node = root; + while (node != null || !stack.isEmpty()) { + while (node != null) { + stack.push(node); + node = node.left; + } + node = stack.pop(); + res.add(node.val); + node = node.right; + } + return res; + } + + +} From c6d58ff77c7e77ba11b39ba86b612fc2b789d2c6 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 22:38:33 +0800 Subject: [PATCH 27/31] Create LeetCode_144_576.java --- Week 02/id_576/LeetCode_144_576.java | 40 ++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100644 Week 02/id_576/LeetCode_144_576.java diff --git a/Week 02/id_576/LeetCode_144_576.java b/Week 02/id_576/LeetCode_144_576.java new file mode 100644 index 000000000..d7b68b4dc --- /dev/null +++ b/Week 02/id_576/LeetCode_144_576.java @@ -0,0 +1,40 @@ +package id_576; + +import java.util.ArrayList; +import java.util.List; +import java.util.Stack; + +public class LeetCode_144_576 { + + // Approach 1: recursion, O(n) + public List preorderTraversal1(TreeNode root) { + List res = new ArrayList<>(); + helper(root, res); + return res; + } + + private void helper(TreeNode root, List res) { + if (root == null) return; + res.add(root.val); + helper(root.left, res); + helper(root.right, res); + } + + // Approach 2: stack with manual, O(n) + public List preorderTraversal2(TreeNode root) { + List res = new ArrayList<>(); + if (root == null) return res; + Stack stack = new Stack<>(); + TreeNode node = root; + while (node != null || !stack.isEmpty()) { + while (node != null) { + res.add(node.val); + stack.push(node); + node = node.left; + } + node = stack.pop().right; + } + return res; + } + +} From 2b55d3deaf06cabcd532b5dd489c0be04430d0cc Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 22:39:08 +0800 Subject: [PATCH 28/31] Create LeetCode_145_576.java --- Week 02/id_576/LeetCode_145_576.java | 46 ++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) create mode 100644 Week 02/id_576/LeetCode_145_576.java diff --git a/Week 02/id_576/LeetCode_145_576.java b/Week 02/id_576/LeetCode_145_576.java new file mode 100644 index 000000000..1b9e07759 --- /dev/null +++ b/Week 02/id_576/LeetCode_145_576.java @@ -0,0 +1,46 @@ +package id_576; + +import javax.naming.InsufficientResourcesException; +import java.util.ArrayList; +import java.util.LinkedList; +import java.util.List; +import java.util.Stack; + +public class LeetCode_145_576 { + + // Approach 1: recursion, O(n) + public List postorderTraversal1(TreeNode root) { + List res = new ArrayList<>(); + helper(root, res); + return res; + } + + private void helper(TreeNode root, List res) { + if (root == null) return; + helper(root.left, res); + helper(root.right, res); + res.add(root.val); + } + + // Approach 2: stack with manual, O(n) + /** + * 更为简洁的写法。这种解法的思想是先序遍历的变形， + * 先序遍历是“根->左->右”，后序遍历是“左->右->根”， + * 那么把先序遍历改成“根->右->左”，再逆序一下就是后序遍历。 + * 没太明白意思？再多练习几遍 + * 画一遍图有些理解了，等于是逆序，从后往前存值。 + */ + public List postorderTraversal2(TreeNode root) { + List res = new LinkedList<>(); + if (root == null) return res; + Stack stack = new Stack<>(); + stack.push(root); + while (!stack.isEmpty()) { + TreeNode node = stack.pop(); + res.add(0, node.val); + if (node.left != null) stack.push(node.left); + if (node.right != null) stack.push(node.right); + } + return res; + } +} From c39b31dbdd61768e41cb423103ff745dec16cb0f Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Mon, 16 Dec 2019 22:41:03 +0800 Subject: [PATCH 29/31] Create LeetCode_590_576.java --- Week 02/id_576/LeetCode_590_576.java | 33 ++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 Week 02/id_576/LeetCode_590_576.java diff --git a/Week 02/id_576/LeetCode_590_576.java b/Week 02/id_576/LeetCode_590_576.java new file mode 100644 index 000000000..e89bc708c --- /dev/null +++ b/Week 02/id_576/LeetCode_590_576.java @@ -0,0 +1,33 @@ +package id_576; + +import java.util.Arrays; + +public class LeetCode_242_576 { + + + public boolean isAnagram1(String s, String t) { + if (s.length() != t.length()) { + return false; + } + + char[] str1 = s.toCharArray(); + char[] str2 = t.toCharArray(); + Arrays.sort(str1); + Arrays.sort(str2); + return Arrays.equals(str1, str2); + } + + // Approach 2: hash、map，统计每个字符的频次 + public boolean isAnagram2(String s, String t) { + if (s.length() != t.length()) { + return false; + } + int[] counter = new int[26]; + for (int i = 0; i < s.length(); i++) { + counter[s.charAt(i) - 'a']++; + counter[t.charAt(i) - 'a']--; + } + for (int count:counter) if (count != 0) return false; + return true; + } +} From 095b85ddf1c2c43607f8f4783174ddfadc4b2148 Mon Sep 17 00:00:00 2001 From: Nicole Lei <40916016+Leith14@users.noreply.github.com> Date: Tue, 17 Dec 2019 13:17:16 +0800 Subject: [PATCH 30/31] Create LeetCode_200_576.java --- Week 03/id_576/LeetCode_200_576.java | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 Week 03/id_576/LeetCode_200_576.java diff --git a/Week 03/id_576/LeetCode_200_576.java b/Week 03/id_576/LeetCode_200_576.java new file mode 100644 index 000000000..a060300f4 --- /dev/null +++ b/Week 03/id_576/LeetCode_200_576.java @@ -0,0 +1,24 @@ +package id_576; + +public class LeetCode_200_576 { + + //Approach 1: floodfill, O(M * N) + char[][] g; + public int numIslands(char[][] grid) { + int islands = 0; + g = grid; + for (int i=0; i Date: Tue, 17 Dec 2019 13:17:50 +0800 Subject: [PATCH 31/31] Create LeetCode_102_576.java --- Week 03/id_576/LeetCode_102_576.java | 48 ++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 Week 03/id_576/LeetCode_102_576.java diff --git a/Week 03/id_576/LeetCode_102_576.java b/Week 03/id_576/LeetCode_102_576.java new file mode 100644 index 000000000..e31eef81c --- /dev/null +++ b/Week 03/id_576/LeetCode_102_576.java @@ -0,0 +1,48 @@ +package id_576; + +import jdk.nashorn.api.tree.Tree; + +import java.time.temporal.Temporal; +import java.util.ArrayList; +import java.util.Deque; +import java.util.LinkedList; +import java.util.List; + +public class LeetCode_102_576 { + + //Approach 1: BFS, O(n) + public List> levelOrder1(TreeNode root) { + List> res = new ArrayList<>(); + if (root == null) return res; + Deque queue = new LinkedList<>(); + queue.add(root); + while (!queue.isEmpty()) { + List tmp = new ArrayList<>(); + int cnt = queue.size(); + for (int i = 0; i < cnt; i++) {//为什么直接写queue.size()会报错？ + // 因为queue.size()在循环体里值不会改变，需要借助变量cnt改变 + TreeNode node = queue.poll(); + tmp.add(node.val); + if (node.left != null) queue.add(node.left); + if (node.right != null) queue.add(node.right); + } + res.add(tmp); + } + return res; + } + + //Approach 2: DFS, O(n) + public List> levelOrder2(TreeNode root) { + List> res = new ArrayList<>(); + helper(res, root, 0); + return res; + } + + private void helper(List> res, TreeNode root, int level) { + if (root == null) return; + if (res.size() == level) res.add(new LinkedList<>()); + res.get(level).add(root.val); + helper(res, root.left, level + 1); + helper(res, root.right, level + 1); + } +}