3Sum Closest

问题描述

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).

实现方案

def three_sum_closest(nums, target):
    nums.sort()
    result = nums[0] + nums[1] + nums[-1]
    for i in range(len(nums) - 1):
        if i == 0 or (i != 0 and nums[i] != nums[i - 1]):
            low = i + 1
            high = len(nums) - 1
            while low < high:
                s = nums[i] + nums[low] + nums[high]
                if s == target:
                    return target
                if s < target:
                    low += 1
                else:
                    high -= 1
                if abs(s - target) < abs(result - target):
                    result = s
    return result


print three_sum_closest([0, 2, 1, -3], 1)