三元組相加得到結果最接近target

三元組相加得到結果最接近target

3SumClosest

• 給定一個數組，選擇三個元素相加，結果必須爲全部三元組中最接近target的值，返回這個三元組的和。

• 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.

example 1

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).

input: [-1, 2, 1, -4], 1
output: 2

思路

1. 思路參照三元組相加得到target

2. 只須要將上述文章思路2中換成：第二次循環找到 三元組的和 最接近target的組合便可。

代碼

class Solution(object):
    def threeSumClosest(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        nums.sort()
        closest = nums[0] + nums[1] + nums[2]
        for i in range(len(nums)):
            j, k = i + 1, len(nums) - 1
            while j < k:
                value = nums[i] + nums[j] + nums[k]
                closest = value if abs(target - value) < abs(target - closest) else closest
                if value == target:
                    return target
                elif value > target:
                    k -= 1
                else:
                    j += 1
        return closest

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