MergeSort错误

Question

我的合并排序代码如下。当我在测试数组5，3，2，1，8，4，9，11上运行它时，我得到了错误："TypeError：'NoneType‘类型的对象没有len()"，它在merge方法的开头抛出。我的打印输出如下：-正在尝试合并左侧:5-正在尝试合并右侧:3-合并数组: 3，5-正在尝试合并左侧:2-正在尝试合并右侧:1-合并数组: 1，2-正在尝试合并左侧:无-正在尝试合并右侧:无

看起来我已经成功地合并了前4个元素，然后它尝试合并两个空元素，我不知道为什么会这样。

def mergeSort(array, size):
    # BASE CASE
    if size <= 1:
        return array

    #split in half recursively and once they're all one element, merge
    else:
        left = mergeSort(array[:size / 2], size / 2)
        right = mergeSort(array[size / 2:], size / 2)

        temp = merge(left, right)
        print "merged array: ", temp

def merge(leftElements, rightElements):
    print("trying to merge left: "), leftElements
    print("trying to merge right: "), rightElements
    lengthLeft = len(leftElements)
    lengthRight = len(rightElements)
    mergedArray = []

    # - i is the index for leftElements
    # - j is the index for rightElements

    i = 0
    j = 0
    while (i < lengthLeft):
        while (j < lengthRight):
            if leftElements[i] < rightElements[j]:
                mergedArray.append(leftElements[i])
                i += 1
            elif leftElements[i] > rightElements[j]:
                mergedArray.append(rightElements[j])
                j += 1
            else:
                mergedArray.append(leftElements[i])
                mergedArray.append(rightElements[j])
                i += 1
                j += 1

            booleanLeft = i >= lengthLeft
            booleanRight = j >= lengthRight

            if ((i >= lengthLeft) or (j >= lengthRight)):
                break
        if ((i >= lengthLeft) or (j >= lengthRight)):
            break

    # now need to account for the case when one array clears before the other
    if (i < lengthLeft):
        for q in range(i, lengthLeft):
            mergedArray.append(leftElements[q])
    if (j < lengthRight):
        for q in range(j, lengthRight):
            mergedArray.append(rightElements[q])
    return mergedArray

print(mergeSort([5, 3, 2, 1, 8, 4, 9, 11], 8))

Answer 1

您的mergeSort函数不返回任何内容

因此，根据定义，它现在返回，这就是nones的来源。

只需添加一个回车符，您就应该没问题。