16. 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 len = nums.size();
        sort(nums.begin(), nums.end());
        int closestVal = INT_MAX;
        int closestSum = 0;
        for(int i=0; i < len-2; i++)
        {
            int j = i+1;
            int k = len - 1;
            while(j < k)
            {
                int sum = nums[i] + nums[j] + nums[k];
                int val = abs(sum - target);
                if(val < closestVal)
                {
                    closestVal = val;
                    closestSum = sum;
                }
                if(sum > target)
                {
                    k--;
                }else j++;
            }
        }
        return closestSum;
    }
};