-
Notifications
You must be signed in to change notification settings - Fork 4
Expand file tree
/
Copy pathLeetCode416.java
More file actions
63 lines (57 loc) · 1.95 KB
/
Copy pathLeetCode416.java
File metadata and controls
63 lines (57 loc) · 1.95 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
package LeetCode.array;
public class LeetCode416 {
public boolean canPartition(int[] nums) {
if(nums == null) return false;
int sum = 0;
for(int num : nums) sum += num;
if((sum & 1) == 1) return false;
sum /= 2;
// dp[i][j]表示nums[0 - i-1]组成 j 值的可能性
boolean[][] dp = new boolean[nums.length+1][sum+1];
dp[0][0] = true;
for(int i = 1; i < dp.length; i++){
for(int j = 1; j < dp[0].length; j++){
dp[i][j] = dp[i-1][j];
if(j >= nums[i-1]){
dp[i][j] = dp[i][j] || dp[i-1][j-nums[i-1]];
}
}
}
return dp[nums.length][sum];
}
// 空间优化
public boolean canPartition2(int[] nums) {
if(nums == null) return false;
int sum = 0;
for(int num : nums) sum += num;
if((sum & 1) == 1) return false;
sum /= 2;
boolean[] dp = new boolean[sum+1];
dp[0] = true;
for(int i = 1; i <= nums.length; i++){
for(int j = dp.length-1; j >= 1; j--){
if(j >= nums[i-1]){
dp[j] = dp[j] || dp[j-nums[i-1]];
}
}
dp[0] = false;
}
return dp[sum];
}
// 递归解法
public boolean canPartition3(int[] nums) {
if(nums == null) return false;
int sum = 0;
for(int num : nums) sum += num;
if((sum & 1) == 1) return false;
return recur(nums, sum/2, nums.length-1);
}
private boolean recur(int[] nums, int target, int index){
if(target == 0) return true;
if(index < 0 || target < 0) return false;
if(recur(nums, target-nums[index], index-1)) return true;
int j = index-1;
while (j >= 0 && nums[j] == nums[index]) j--;
return recur(nums, target, j);
}
}