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
| public class FourSum {
public List<List<Integer>> fourSum(int[] nums, int target) {
List<List<Integer>> result = new ArrayList<List<Integer>>();
if (nums == null || nums.length < 4) {
return result;
}
Arrays.sort(nums);
int l = nums.length;
for (int i = 0; i < l - 3; i++) {
if (i > 0 && nums[i] == nums[i - 1]) {
continue;
}
for (int j = i + 1; j < l - 2; j++) {
if (j > i + 1 && nums[j] == nums[j - 1]) {
continue;
}
for (int k = j + 1; k < l - 1; k++) {
if (k > j + 1 && nums[k] == nums[k - 1]) {
continue;
}
int left = target - nums[i] - nums[j] - nums[k];
if (helper(k + 1, l - 1, nums, left)) {
List<Integer> r = new ArrayList<Integer>();
r.add(nums[i]);
r.add(nums[j]);
r.add(nums[k]);
r.add(left);
result.add(r);
}
}
}
}
return result;
}
private boolean helper(int start, int end, int[] nums, int target) {
while (start <= end) {
int middle = (start + end) / 2;
if (nums[middle] == target) {
return true;
}
if (nums[middle] > target) {
end = middle - 1;
} else {
start = middle + 1;
}
}
return false;
}
}
|