class Solution:
    def threeSumClosest(self, nums: List[int], target: int) -> int:
        if not nums or len(nums) < 3:
            return -1

        nums.sort()
        ans = float("inf")

        for idx, first_num in enumerate(nums):
            ans = self.two_sum(nums, target, ans, first_num, idx+1, len(nums)-1)    

        return ans

    def two_sum(self, nums, target, ans, first_num, left, right):
        while(left < right):
            if first_num + nums[left] + nums[right] == target:
                return target
            elif first_num + nums[left] + nums[right] < target:
                ans = self.find_closest(ans, first_num + nums[left] + nums[right], target)
                left += 1
            else: # if first_num + nums[left] + nums[right] > target:
                ans = self.find_closest(ans, first_num + nums[left] + nums[right], target)
                right -= 1
        else:
            return ans      

    def find_closest(self, a, b, target):
        if abs(a - target) <= abs(b - target):
            return a
        else:
            return b