16. 3Sum Closest

Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

 

Example 1:

Input: nums = [-1,2,1,-4], target = 1 Output: 2 Explanation: The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

 

Constraints:

• 3 <= nums.length <= 10^3
• -10^3 <= nums[i] <= 10^3
• -10^4 <= target <= 10^4

class Solution(object):
    def threeSumClosest(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        
        nums = sorted(nums)

        res = nums[0]+nums[1]+nums[2]

        for i in range(0, len(nums)):
            left = i+1
            right = len(nums)-1

            while left < right:
                sums = nums[i] + nums[left] + nums[right]

                if sums == target:
                    return sums
                elif abs(target - res) > abs(target - sums):
                    res = sums        
                if sums < target:
                    left += 1
                elif sums > target:
                    right -=1
                    
        return res

 

15번 문제와 비슷하게 2개의 포인터를 사용하면 쉽게 풀 수 있었다.