3sum-closest.py

class Solution:
    def threeSumClosest(self, nums, target):
        nums.sort()

        result = None

        for pos in range(len(nums) - 2):
            left, right = pos + 1, len(nums) - 1

            while left < right:
                cur_sum = nums[pos] + nums[left] + nums[right]

                if cur_sum < target:
                    left += 1
                elif cur_sum > target:
                    right -= 1
                else:
                    return cur_sum

                result = min(
                    result if result is not None else float("+inf"),
                    cur_sum,
                    key=lambda x: abs(target - x),
                )

        return result if result is not None else 0


class TestSolution:
    def setup(self):
        self.sol = Solution()

    def test_empty(self):
        assert self.sol.threeSumClosest([], 0) == 0
        assert self.sol.threeSumClosest([1], 0) == 0
        assert self.sol.threeSumClosest([1, 2], 0) == 0

    def test_custom1(self):
        assert self.sol.threeSumClosest([1, 2, 3], 0) == 6

    def test_custom2(self):
        assert self.sol.threeSumClosest([-1, 2, 1, -4], 1) == 2

    def test_custom3(self):
        assert self.sol.threeSumClosest([0, 1, 2], 3) == 3

    def test_custom4(self):
        assert self.sol.threeSumClosest([1,1,1,0], -100) == 2

    def test_custom5(self):
        assert self.sol.threeSumClosest([0,2,1,-3], 1) == 0