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).

public int ThreeSumClosest(int[] nums, int target) {        Array.Sort(nums);        int size = nums.Count();        int res = Int32.MaxValue;        for(int i =0;i< size-1;i++)        {            int last = Int32.MaxValue;            int dif = target - nums[i];            int left = i+1;            int right = size-1;            while(left < right)            {                int a = nums[left] + nums[right] - dif;                if(a==0) return target;                if(Math.Abs(a)< last )                {                    res = Math.Abs(a)>Math.Abs(res) ?res :a;                    last = Math.Abs(a);                }                if(a<0) left++;                else right--;            }                    }        return res+target;    }