Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

Example:

Given array nums = [-1, 2, 1, -4], and target = 1.

The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
 

這個題和Leetcode15的思路基本類似，就是在前面那個題目的基礎上加上了一個判斷求值。

1）

import java.util.*;
public class Solution {
    public int threeSumClosest(int[] nums, int target) {
        Arrays.sort(nums);
        int len = nums.length;
        if(len < 3){
            return 0;
        }
        int Min = nums[0] + nums[1] + nums[2];
        for(int left = 0 ; left < len - 2 ; left++){
            int mid = left + 1;
            int right = len - 1;
            while(mid < right){
                int tmp = target - nums[left];
                if(Math.abs(Min - target) > Math.abs(tmp - nums[mid] - nums[right]))
                    Min = nums[mid] + nums[left] + nums[right];
                if(nums[mid] + nums[right] == tmp){
                    return target;
                }else if(nums[mid] + nums[right] < tmp){
                    mid++;
                }else{
                    right--;
                }
            }
        }
        return Min;
    }
}
 

時間複雜度：O（n2）