3SumClosest.cpp

 int threeSumClosest(vector<int>& nums, int target) {
            if(nums.size() < 3) return 0;
    int closest = nums[0]+nums[1]+nums[2];
    sort(nums.begin(), nums.end());
    for(int first = 0 ; first < nums.size()-2 ; ++first) {
        if(first > 0 && nums[first] == nums[first-1]) continue;
        int second = first+1;
        int third = nums.size()-1;            
        while(second < third) {
            int curSum = nums[first]+nums[second]+nums[third];
            if(curSum == target) return curSum;
            if(abs(target-curSum)<abs(target-closest)) {
                closest = curSum;
            }
            if(curSum > target) {
                --third;
            } else {
                ++second;
            }
        }
    }
    return closest;

    }