Subject: https://leetcode-cn.com/problems/3sum/
Answer: double pointer
public List<List<Integer>> threeSum(int[] nums) {
Arrays.sort(nums);
int len = nums.length;
List<List<Integer>> result = new ArrayList<>();
for(int i=0;i<len;i++){
if(i>0 && nums[i] == nums[i-1]){
continue;
}
if(nums[i]>0) break;
int right = len-1;
int target = -nums[i];
for(int left = i+1;left<len;left++){
if(left>i+1 && nums[left] == nums[left-1]){
continue;
}
if(nums[i]+nums[left]>0) break;
while (left<right && nums[left]+nums[right]>target){
right--;
}
if(left == right) break;
if(nums[left] +nums[right] == target){
List<Integer> list = new ArrayList<>();
list.add(nums[i]);
list.add(nums[left]);
list.add(nums[right]);
result.add(list);
}
}
}
return result;
}