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).

思路1：类似3Sum，区别是不需要去重，另外需要维护一个最小差值。

import java.util.Arrays;public class Solution {	public int threeSumClosest(int[] num, int target) {		int n = num.length;		Arrays.sort(num);		int min = Integer.MAX_VALUE;		int result = 0;		for (int i = 0; i < n; i++) {			int start = i + 1, end = n - 1;			int sum = target - num[i];			int cur = 0;			while (start < end) {				cur = num[start] + num[end];				if (Math.abs(cur + num[i] - target) < min) {					min = Math.abs(cur + num[i] - target);					result = cur + num[i];				}				if (cur < sum)					start++;				else if (cur > sum)					end--;				else {					start++;					end--;				}			}		}		return result;	}	public static void main(String[] args) {		System.out.println(new Solution().threeSumClosest(new int[] { -1, 2, 1,				-4 }, 1));		System.out.println(new Solution().threeSumClosest(				new int[] { 1, 2, 3, }, 100));	}}