Question

我对合并排序感兴趣。我编写了合并步骤以升序排序，并且可以正常工作（请参见下面的代码）。但是，当我尝试调整代码以使其以递减的方式排序时，我无法做到。我想反转i和j，但似乎不起作用。有人有什么想法吗？

def fusion(A,low,mid,high):
    aux = [2,7,8,3,6,9]
    i = low
    j = mid+1
    for k in range(low,high,1):
        if i>mid:
            A[k] = aux[j]
            j = j+1
        elif j > high:
            A[k] = aux[i]
            i = i+1
        elif aux[i] <= aux[j]:
            A[k] = aux[i]
            i = i+1
        else:
            A[k] = aux[j]
            j = j+1
    return A
fusion([2,7,8,3,6,9],0,2,5)

输出为2,3,6,7,8,9，但我想要9,8,7,6,3,2

Answer 1

这是“反向”变体：

def fusion(A, low, mid, high):
    aux = A[::-1]  # reverse A
    i = low
    j = mid + 1
    for k in range(low, high, 1):
        if i > mid:
            aux[-k - 1] = A[j]
            j += 1
        elif j > high:
            aux[-k - 1] = A[i]
            i += 1
        elif A[i] <= A[j]:
            aux[-k - 1] = A[i]
            i += 1
        else:
            aux[-k - 1] = A[j]
            j += 1
    return aux


print(fusion([2, 7, 8, 3, 6, 9], low=0, mid=2, high=5))

或者反转range()：

def fusion(A, low, mid, high):
    aux = A[::-1]  # reverse A
    i = low
    j = mid + 1
    for k in range(high, low, -1):
        if i > mid:
            aux[k] = A[j]
            j += 1
        elif j > high:
            aux[k] = A[i]
            i += 1
        elif A[i] <= A[j]:
            aux[k] = A[i]
            i += 1
        else:
            aux[k] = A[j]
            j += 1
    return aux

或者只是...

list(reversed(fusion([2, 7, 8, 3, 6, 9], 0, 2, 5)))

合并排序：如何以递减的方式排序？

1 个答案: