题意

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.

给定一个数组及一个目标值，找出三个数，使它们的和与目标值的差值最小，输出它们的和。

解法

与上一题3Sum一样，遍历第一个数，然后用双指针算法遍历剩下两个数，随时比较它们与目标值的差值。

class Solution

{

public:

    int threeSumClosest(vector<int>& nums, int target)

    {

	    sort(nums.begin(),nums.end());

	    int	diff = 0x7fffffff;

	    int	ans = 0;

	    for(int i = 0;i < nums.size();i ++)

	    {

		    int	j = i + 1;

		    int	k = nums.size() - 1;

		    while(j < k)

		    {

			    int	sum = nums[i] + nums[j] + nums[k];

			    if(abs(sum - target) < diff)

			    {

				    diff = abs(sum - target);

				    ans = sum;

			    }

			    if(sum < target)

				    j ++;

			    else

				    k --;

		    }

	    }

	    return	ans;

    }

};