leetcode133:3sum-closest

题目描述

给出含有n个整数的数组s，找出s中和加起来的和最接近给定的目标值的三个整数。返回这三个整数的和。你可以假设每个输入都只有唯一解。

   例如，给定的整数 S = {-1 2 1 -4}, 目标值 = 1.↵↵   最接近目标值的和为 2. (-1 + 2 + 1 = 2).

 

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).

示例1

输入

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[0,0,0],1

输出

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0
链接：https://www.nowcoder.com/questionTerminal/291a866d7c904563876b373b0b157dde?f=discussion
来源：牛客网

class Solution {

public:

    int threeSumClosest(vector<int> &num, int target) {

        int n = num.size();

        int result = num[0] + num[1] + num[n-1];

        sort(num.begin(),num.end());

        for(int i=0;i<n-2;i++)

        {

            int start = i + 1;

            int end = n - 1;

            while(start < end)

            {

                int sum = num[i] + num[start] + num[end];

                if(sum < target)

                    start++;

                else

                    end--;

                 

                if(abs(sum-target) < abs(result-target))

                    result = sum;

            }

        }

        return result;

    }

};