如何在Python中返回递归函数的列表

我试图从函数返回一个字符串列表，该函数计算没有连续 0 的所有可能排列。

为此，我正在运行一个有效的递归函数，但我需要创建一个包含结果的列表。

# Function to print all n–digit binary strings without any consecutive 0's
def countStrings(n, out="", last_digit=0):
    # if the number becomes n–digit, print it
    
    if n == 0:
        print(out)
        return
    
    # append 0 to the result and recur with one less digit
    countStrings(n - 1, out + '1', 0)
    
 
    # append 1 to the result and recur with one less digit
    # only if the last digit is 0
    if last_digit == 0:
        countStrings(n - 1, out + '0', 1)

当我运行它时，例如：a = countStrings(3)，它打印所有可能性，但变量“a”返回为“None”：

results:

111
110
101
011
010

type(a): Nonetype

我尝试在某些地方插入附加，但没有结果

我不知道我错过了什么

这是您正在寻找的吗？

# Function to print all n–digit binary strings without any consecutive 0's
def countStrings(n, out="", last_digit=0, acc=[]):
    # if the number becomes n–digit, print it
    
    if n == 0:
        print(out)
        acc.append(out)
        return acc
    
    # append 0 to the result and recur with one less digit
    countStrings(n - 1, out + '1', 0, acc)
    
 
    # append 1 to the result and recur with one less digit
    # only if the last digit is 0
    if last_digit == 0:
        countStrings(n - 1, out + '0', 1, acc)
    return acc

acc = countStrings(3)
print('acc', acc)

Output:

111
110
101
011
010
('acc', ['111', '110', '101', '011', '010'])