Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note:
For example, given array S = {-1 0 1 2 -1 -4},
A solution set is:
(-1, 0, 1)
(-1, -1, 2)
package com.mingxin.leetcode.leet_15;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Created by Administrator on 2016/1/25.
*/
public class ThreeSum {
public static void main(String[] args){
int num[] = {-1, -20, -5, -7, 0, 1, 2, 7, 6, 10};
List<List<Integer>> result = threeSum(num);
for(List<Integer> item1:result){
System.out.println("{" + item1.get(0) + ", " + item1.get(1) + ", " + item1.get(2) + "}");
}
}
public static List<List<Integer>> threeSum(int[] nums) {
List<List<Integer>> res = new ArrayList<List<Integer>>();
if(nums.length<3||nums == null){
return new ArrayList<List<Integer>>();
}
Arrays.sort(nums);
for(int i = 0; i <= nums.length-3; i++){
if(i==0||nums[i]!=nums[i-1]){
int low = i+1;
int high = nums.length-1;
while(low<high){
int sum = nums[i]+nums[low]+nums[high];
if(sum == 0){
ArrayList<Integer> unit = new ArrayList<Integer>();
unit.add(nums[i]);
unit.add(nums[low]);
unit.add(nums[high]);
res.add(unit);
low++;
high--;
while(low<high&&nums[low]==nums[low-1]){
low++;
}
while(low<high&&nums[high]==nums[high+1]){
high--;
}
}else if(sum > 0){
high --;
}
else{
low ++;
}
}
}
}
return res;
}
}
原文：http://www.cnblogs.com/kniught-ice/p/5159581.html