这个问题已经在这里有了答案：            >            Finding three elements in an array whose sum is closest to a given number                                    13个
在阅读了约Finding three elements in an array whose sum is closest to a given number之后,这是我尝试实现这种算法的尝试

def findThree(seq, goal):

    # initialize the differences 
    goalDifference = float("inf")
    dl = -1
    dr = -1
    dx = -1

    for x in range(len(seq)-1):

        left = x+1
        right = len(seq)-1


        while (left < right):

            # if the absolute value of the previous set and the goal is less than the current goalDifference,
            # keep track of the new set
            if(abs(goal - (seq[left] + seq[right] + seq[x])) < goalDifference):
                dl = left
                dr = right
                dx = x

            tmp = seq[left] + seq[right] + seq[x]

            if tmp > goal:
                right -= 1
            elif tmp < goal:
                left += 1
            else:
                return [seq[left],seq[right],seq[x]]

    # if no match is found, return the closest set
    return [seq[dl],seq[dr], seq[dx]]

在给定的条件下,该算法非常适合查找精确解

arr = [89, 120, 140, 179, 199, 259, 259, 259, 320, 320]

findThree(arr, 349) // want to get [120, 140, 89]
>> [120, 140 89] // success

findThree(arr, 439) // want to get [140, 179, 120]
>> [140, 179,120] // success

但是,当我想查看是否返回最接近的值时,它会返回

findThree(arr, 350) // only 1 more than 349, should return [120, 140, 89]
>> [320, 320, 259] // fail

findThree(arr, 440) // only 1 more than 439, should return [140, 179, 120]
>> [320, 320, 259] // fail

看来,当我希望它返回“最接近的”元素时,它总是返回[320、320、259].我已经看了几个小时的代码,但仍然无法找出问题所在.

解决方法:

我迅速查看了您的代码,主要问题是“目标差异”从未改变.

您需要随手挤压“目标差异”,否则所有组合都在“目标差异”之内,显然您最终将得到最后一组作为答案.