反向合并排序答案

【问题标题】：Merge Sort in reverse反向合并排序
【发布时间】：2022-11-28 12:25:43
【问题描述】：

我想使用 mergeSort 对数组进行降序排序

这是我按升序排列的 MergeSort 实现的代码

def MergeSort(B):
        if len(B) <= 1: 
            return 
        mid = len(B)//2
        half1 = B[:mid]
        half2 = B[mid:]
        reverseSort(half1)
        reverseSort(half2)
        merge(half1,half2,B)
    def merge(half1, half2, B):
        i=0; j1=0; j2=0
        while j1<len(half1) and j2<len(half2):
            if half1[j1] < half2[j2]:
                B[i] = half1[j1]
                j1 += 1; i += 1
            else:
                B[i] = half2[j2]
                j2 += 1; i += 1
        while j1 > len(half1):
            B[i] = half1[j1]
            j1 += 1; i += 1
        while j2 > len(half2):
            B[i] = half2[j2]
            j2 += 1; i += 1

我尝试将以下 if 语句更改为此如果 half1[j1] < half2[j2]:

但输出不正确

基本上我想要以下

B=["cat", "ca", "can", "cat", "cat"]
MergeSortReverse(B)
print(B) #["cat","cat","cat","can","ca"]

【问题讨论】：

标签： python

【解决方案1】：

如果有帮助，请接受为答案

def merge_sort_descending(arr):
    if len(arr) > 1:
        mid = len(arr) // 2
        left = arr[:mid]
        right = arr[mid:]
        merge_sort_descending(left)
        merge_sort_descending(right)
        i = j = k = 0
        while i < len(left) and j < len(right):
            if left[i] > right[j]:
                arr[k] = left[i]
                i += 1
            else:
                arr[k] = right[j]
                j += 1
            k += 1
        while i < len(left):
            arr[k] = left[i]
            i += 1
            k += 1
        while j < len(right):
            arr[k] = right[j]
            j += 1
            k += 1

B=["cat", "ca", "can", "cat", "cat"]
['cat', 'cat', 'cat', 'can', 'ca']

【讨论】：