Question

您好我是python的新手，我在使用mergesort计数反转问题时遇到了麻烦。错误说“”int“对象是不可迭代的。但是，我不认为我在这个阶段迭代任何数字。因为我被困在这里，我不确定这段代码中是否有更多错误..任何人都可以帮我弄清楚这里发生了什么？非常感谢你。

import sys

def merge_and_count_inversions(x, y):
    sorted_array = [] 
    count = 0 
    i, j = 0, 0
    #print ("inside merge", x, y)
    while i < len(x) and j < len(y):
        if x[i] > y[j]:
            count += len(x) - i
            sorted_array.append(y[j])
            j += 1
        else:
            sorted_array.append(x[i])
            i += 1
    while i < len(x):
        sorted_array.append(x[i])
        i += 1
    while j < len(y):
        sorted_array.append(y[j])
        j += 1
    #print ("overall count = ", count )
    #print ("sorted_array", sorted_array)
    return count, sorted_array

def get_number_of_inversions(a, b, left, right):
    number_of_inversions = 0
    if right - left <= 1:
        return number_of_inversions
    ave = (left + right) // 2
    number_of_inversions_A, a[left:ave] = get_number_of_inversions(a, b, left, ave)
    #print ("left list", a[left : ave])
    #print ("number_of_inversions left half = ", number_of_inversions )
    number_of_inversions_B, a[ave:right] = get_number_of_inversions(a, b, ave, right)
    #print ("right list", a[ave : right])
    #print ("number_of_inversions left + right half = ", number_of_inversions )
    number_of_inversions_C, sorted_list = merge_and_count_inversions(a[left:ave],a[ave:right])
    tot_inversions = number_of_inversions_A + number_of_inversions_B + number_of_inversions_C 
    #print ("number_of_inversions overall = ", number_of_inversions )
    return tot_inversions, sorted_list

input_ = input()
n, *a = list(map(int, input_.split())) #n is the length of a
b = n * [0]
get_number_of_inversions(a, b, 0, len(a))
print(get_number_of_inversions(a, b, 0, len(a)))

错误说：

<ipython-input-60-e1f94361f38a> in get_number_of_inversions(a, b, left, right)
     33     ave = (left + right) // 2
     34     print ("average = ", ave)
---> 35     number_of_inversions_A, a[left:ave] =   get_number_of_inversions(a, b, left, ave)
     36     print ("left list", a[left : ave])
     37     print ("number_of_inversions left half = ", number_of_inversions )

<ipython-input-60-e1f94361f38a> in get_number_of_inversions(a, b, left, right)
     33     ave = (left + right) // 2
     34     print ("average = ", ave)
---> 35     number_of_inversions_A, a[left:ave] =    get_number_of_inversions(a, b, left, ave)
     36     print ("left list", a[left : ave])
     37     print ("number_of_inversions left half = ", number_of_inversions )

TypeError: 'int' object is not iterable

Answer 1

好吧，我不熟悉合并排序算法，但在get_number_of_inversions()中你有两个出口：

首先：

number_of_inversions = 0
if right - left <= 1:
    return number_of_inversions

和

return tot_inversions, sorted_list

您可以在表达式中使用返回值，如：

number_of_inversions_A, a[left:ave] = get_number_of_inversions(a, b, left, ave)

所以有时你会返回一个整数，有时候会返回一个元组。我的猜测是，当你返回一个整数时，就会出现这个错误。

在python中计算反转：int对象不可迭代错误

1 个答案: