Leetcode: 3Sum Closest

3Sum Closest



Similar Problems:


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).

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


## Blog link: https://code.dennyzhang.com/3sum-closest
## Basic Ideas: two sum
## Complexity: Time O(n*n), Space O(1)
class Solution:
    def threeSumClosest(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        import sys
        length = len(nums)
        if length <=2: return sum(nums)
        nums.sort()
        res = sum(nums[0:3])
        for i in range(length-2):
            l, r = i+1, length-1
            while l<r:
                v = nums[i]+nums[l]+nums[r]
                if v == target: return v
                if abs(v-target) < abs(res-target): res = v

                if v > target:
                    # make v smaller
                    r -= 1
                else:
                    l += 1

        return res
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