3Sum

来源：互联网发布：mysql创建表error1064 编辑：程序博客网时间：2024/04/20 15:02

public class Solution {    public ArrayList<ArrayList<Integer>> threeSum(int[] num) {        // Start typing your Java solution below        // DO NOT write main() function       if(num==null||num.length<3)return new ArrayList<ArrayList<Integer>>();       int len = num.length;       Arrays.sort(num);       ArrayList<ArrayList<Integer>> ret = new ArrayList<ArrayList<Integer>>();       for(int i = 0; i < len-2;i++){           if(num[i]>0) break;           int mid = i+1;           int right = len-1;           int sum = -num[i];           while(mid<right){               if(num[mid]+num[right]>sum)right--;               else if(num[mid]+num[right]==sum){                   ArrayList cur = new ArrayList();                   cur.add(num[i]);cur.add(num[mid]);cur.add(num[right]);                   if(!ret.contains(cur))                   ret.add(cur);                   //while(right>0&&num[right-1]==num[right])right--;                   //while(mid<len-1&&num[mid+1]==num[mid])mid++;                   mid++;right--;               }               else mid++;           }           while(i<len-2&&num[i+1]==num[i])i++;       }       return ret;    }}

若判断是否存在要用1852毫秒

直接判断mid和right是否重复不用contains判断要800毫秒。