[LeetCode] 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 ret;
        
        sort(nums.begin(), nums.end());
        
        int mindiff = INT_MAX;
        
        for (int i = 0; i < nums.size(); i++){
            int left = i + 1;
            int right = nums.size() - 1;
            
            while (left < right){
                if (abs(nums[i] + nums[left] + nums[right] - target) < mindiff){
                    mindiff = abs(nums[i] + nums[left] + nums[right] - target);
                    ret = nums[i] + nums[left] + nums[right];
                }
                if (nums[left] + nums[right] < target - nums[i]){
                    left++;
                }else if (nums[left] + nums[right] > target - nums[i]){
                    right--;
                }else{
                    return target;
                }    
            }
        }
        
        return ret;
    }
};