【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).

解题思路：先对数组进行排序，然后遍历数组。寻找和最接近target的数。

演示样例代码：

import java.util.Arrays;
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);//先对nums进行排序
    	for(int i=0;i<length-2;i++)
        {
        	//略过同样的数
        	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,
	        			left++;
	        		else
	        			right--;
	        }
        }
    	return minNum;
    }
}