16. 3Sum Closest

2019-03-28

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:

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Given array nums = [-1, 2, 1, -4], and target = 1.

The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

Code:

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class Solution(object):
    def threeSumClosest(self, nums, target):
        res = []
        nums.sort()
        closestDiff = sys.maxsize  #9223372036854775807
        sign = 1
        for i in range(len(nums)-2):
            l, r = i+1, len(nums)-1

            while l < r:
                s = nums[i] + nums[l] + nums[r]
                if s == target:
                    return s
                if abs(target - s) < closestDiff:
                    sign = -1 if target - s < 0 else 1
                closestDiff = min(abs(target - s), closestDiff)
                if s < target:
                    l +=1
                elif s > target:
                    r -= 1
        return target - (closestDiff * sign)
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