16. 3Sum Closest

差點迷失自我, 其實這個系列應該都是在考你要怎麼去移動你的two pointer

當sum < target, 代表你要讓sum大一點, 移動left,反之就移動right

class Solution
{
public:
    int threeSumClosest(vector<int> &nums, int target)
    {
sort(nums.begin(), nums.end());
        int res = nums[0] +nums[1]+nums[2];
        int min_distance_to_target = INT_MAX;
        for (int i = 0; i < nums.size() - 2; i++)
        {
            if (nums[i] * 3 > target)
                return min(res, nums[i] + nums[i + 1] + nums[i + 2]);
            int l = i + 1;
            int r = nums.size() - 1;
            while (l < r)
            {
                int sum = nums[i] + nums[r] + nums[l];
                if (abs(sum - target) < min_distance_to_target)
                {
                    min_distance_to_target = abs(sum - target);
                    res = sum;
                }
                if (sum < target)
                {
                    l++;
                }
                else
                {
                    r--;
                }
            }
        }
        return res;
    }
};