题解 | #三数之和#

using System;
using System.Collections.Generic;


class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param num int整型一维数组 
     * @return int整型二维数组
     */
    public List<List<int>> threeSum (List<int> num) {
        num.Sort();
        List<List<int>> res = new List<List<int>>();
        for(int i = 0; i < num.Count - 2; ){
            int left = i + 1;
            int right = num.Count - 1;
            while(left < right){
                int cur = num[i] + num[left] + num[right];
                if(cur > 0) right--;
                else if(cur < 0) left++;
                else{
                    List<int> newres = new List<int>{num[i], num[left], num[right]};
                    newres.Sort();
                    res.Add(newres);
                    int newleft = left + 1;
                    while(newleft < right && num[newleft] == num[left]) newleft++;
                    left = newleft;
                }
            }
            int newi = i + 1;
            while(newi < num.Count - 2 && num[newi] == num[i]) newi++;
            i = newi;
        }
        return res;
    }
}