【LeetCode OJ 016】3Sum Closest

题目链接：https://leetcode.com/problems/3sum-closest/

题目：Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

For example, given array S = {-1 2 1 -4}, and target = 1.    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

题意：给定一个数组和一个target数，找出三个数使得他们的和最接近于target。

public class Solution{    public int threeSumClosest(int[] nums, int target)    {    int length=nums.length;    int minNum=Integer.MAX_VALUE;    int tempsubNum=Integer.MAX_VALUE;     Arrays.sort(nums);    for(int i=0;i<length-2;i++)        {        //略过相同的数        if(i!=0&&nums[i]==nums[i-1])        {        continue;        }        int left=i+1;         int right=length-1;                while(left<right)        {        int a1=nums[left];        int a2=nums[right];        int sum=a1+a2+nums[i];        int subNum=Math.abs(sum-target);        //当前的和值sum离target更近一点        if(subNum<=tempsubNum)        {        tempsubNum=subNum;  //保存这一步中的sum-target的差值        minNum=sum;        }        if(sum-target<0) //说明sum<target,要往右移动，使得sum变大才能更接近target        left++;        else//反之，往左移动        right--;        }        }    return minNum;           }}