【leetcode】第15题：3sum(medium)

package com.leetcode;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

public class Solution14 {
public static List< List< Integer >> threeSum(int [ ] nums){
//先将数组排序
Arrays.sort(nums);
List<List< Integer >> list = new ArrayList<List< Integer >>();
for(int i = 0; i< nums.length; i++){
if(i == 0||(i > 0 && nums[ i ] != nums[ i-1] )){
int low = i+1, high = nums.length-1, sum = 0-nums[i];
while(low<high){
if( nums[low] + nums[high] == sum){
list.add(Arrays.asList( nums[i], nums[low], nums[high]));
//判断下一个元素是否和这个元素相同，如果相同就继续low++遍历,这就是为什么药排序的原因
//排完序后相同的元素都在一起
while( low < high && nums[ low ] == nums[ low+1 ]) low++;
while(high > low && nums[ high ] == nums[high-1] ) high--;
low++;high--;
//判断向前的和是否小于sum，如果小了，那么就是nums[low]小了
} else if( nums[low] + nums[high] < sum ){
low++;
//反之就是high大了
}else{ high--;}
}
}
}
return list;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
int[ ] nums = {-1, 0 ,1, 2, -1, -4};
List< List< Integer >>  list = Solution14.threeSum(nums);
Iterator it = list.iterator();
for(int i = 0; i< list.size() ; i++){
System.out.println(list.get(i));
}
}
}