题解 | #数组中相加和为0的三元组#

先对数组进行排序，再使用双指针 ，代码如下

import  java.util.*;
public class Solution {
      public ArrayList<ArrayList<Integer>> threeSum(int[] num) {

        ArrayList<ArrayList<Integer>>  res = new ArrayList<>();
        int len = num.length;
        if(len<3){
            return res;
        }
        Arrays.sort(num);
        for (int i = 0; i < len-2; i++) {
              if (num[i]>0) break;
              if (i>0&&num[i] == num[i-1]) continue;
              int left = i+1;
              int right = len-1;
              while (left<right){
                  int sum  = num[i] + num[left] + num[right];
                  if (sum>0){
                      while (left<right&&num[right] == num[--right]);
                  }else  if (sum<0){
                      while (left<right &&num[left] == num[++left]);
                  }else {
                      ArrayList<Integer> list = new ArrayList<>();
                      list.add(num[i]);
                      list.add(num[left]);
                      list.add(num[right]);
                      res.add(list);
                      while (left<right&&num[right] == num[--right]);
                      while (left<right &&num[left] == num[++left]);

                  }
              }
        }
        return  res;
    }
}