求无序数组中三个元素相加与目标数最接近的三元素之和

/************************************************************************************************
**description:给定一个无序数组和一个目标数，要求返回数组中三个元素相加与目标数最接近的三元素之和
**            如：Input: a={-1 2 1 -4},target=1    Output: 2 (-1 + 2 + 1 = 2)
*************************************************************************************************/

//先排序，然后对有序数组遍历，内层夹逼。
//时间复杂度O(n^2)，空间复杂度O(1)

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int threeSumClosest(vector<int> &arr, int target)
{
int result = 0;
int minDiff = 100;
if (arr.size() < 3)
return result;
sort(arr.begin(), arr.end());
for (int i = 0; i < arr.size() - 2; i++)
{
if (i > 0 && arr[i] == arr[i - 1])
continue;
int m = i + 1;
int n = arr.size() - 1;
while (m < n)
{
int diff = abs(target - arr[i] - arr[m] - arr
);
if (diff < minDiff)
{
result = arr[i] + arr[m] + arr
;
minDiff = diff;
}
if (arr[i] + arr[m] + arr
< target)
m++;
else
n--;
4000
}
}
return result;
}