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).

题目要求找出数组中三个元素相加的和最接近目标值，然后返回这三个数的值。

先对数组进行排序，然后固定第一个数，第二、三个数在数组前后移动，求出三个数之和，并和目标值比较，判断最接近目标值的三个数的和即可，时间复杂度O(n^2)，代码如下：

public class Solution{
	public int threeSumClosest(int[] num,int target){
		int min=Integer.MAX_VALUE;
		int result=0;

		Arrays.sort(num);

		int len=num.length;
		for(int i=0;i<len;i++){
			int j=i+1;
			int k=len-1;
			while(j<k){
				int sum=num[i]+num[j]+num[k];
				int diff=Math.abs(sum-target);

				if(diff==0){
					return sum;
				}

				if(diff<min){
					min=diff;
					result=sum;
				}
				if(sum<=target){
					j++;
				}else{
					k--;
				}
			}
		}
		return result;
	}
}

---EOF---

【LeetCode】3Sum Closest