algorithm004-01 · heyucool · Dec 15, 2019
diff --git a/Week 08/id_161/ReverWords b/Week 08/id_161/ReverWords
@@ -0,0 +1,18 @@
+class Solution {
+    public String reverseOnlyLetters(String S) {
+        Stack<Character> letters = new Stack();
+        for (char c: S.toCharArray())
+            if (Character.isLetter(c))
+                letters.push(c);
+
+        StringBuilder ans = new StringBuilder();
+        for (char c: S.toCharArray()) {
+            if (Character.isLetter(c))
+                ans.append(letters.pop());
+            else
+                ans.append(c);
+        }
+
+        return ans.toString();
+    }
+}
diff --git a/Week 08/id_161/UniqueChars b/Week 08/id_161/UniqueChars
@@ -0,0 +1,18 @@
+class Solution {
+    public int firstUniqChar(String s) {
+        HashMap<Character, Integer> count = new HashMap<Character, Integer>();
+        int n = s.length();
+        // build hash map : character and how often it appears
+        for (int i = 0; i < n; i++) {
+            char c = s.charAt(i);
+            count.put(c, count.getOrDefault(c, 0) + 1);
+        }
+
+        // find the index
+        for (int i = 0; i < n; i++) {
+            if (count.get(s.charAt(i)) == 1) 
+                return i;
+        }
+        return -1;
+    }
+}