Leetcode122: 3Sum Closest

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).

class Solution {
public:
int threeSumClosest(vector<int>& nums, int target) {
int n = nums.size();
int mindiff = INT_MAX;
int res;
sort(nums.begin(), nums.end());
for(int i = 0; i < n-2; i++)
{
if(i>0 && nums[i]==nums[i-1])
continue;
int j = i+1;
int k = n-1;
while(j<k)
{
int sum = nums[i]+nums[j]+nums[k];
if(sum<target)
{
if((target-sum)<mindiff)
{
mindiff = target-sum;
res = sum;
}
j++;
}
else if(sum>target)
{
if((sum-target)<mindiff)
{
mindiff = sum-target;
res = sum;
}
k--;
}
else
return sum;
}
}
return res;
}
};