字符串中所有字符的排列

Question

我试图使用不同字符串中的字符生成一个序列。

示例：

["abcdef", "xyz", "-/", "98765"]

• Output：ax-9,ax-8,ax-7,ax-6,ax-5,ax/9,ax/8,ax/7,ax/6,ax/5,ay-9,ay-8,ay-7,ay-6,ay-5

输入：

代码：

def print_taxi_serial_numbers(params, code, level, offsets, n):
    params_length = len(params)
    print("TT11 :: ", code, level, offsets)
    if level == params_length-1:
        for c in params[level]:
            print("{}{}".format(code,c))
    else:
        while True:
            print("LEVEL :: ", level)
            if level == 0:
                code = ""
            code = "{}{}".format(code, params[level][offsets[level]])
            offsets[level] += 1
            level = level + 1
            if level >= params_length:
                print("LEVEL1 :: ", level, " params_length :: ", params_length, " yy :: ", offsets, " zz ", params)
                return
            print_taxi_serial_numbers(params, code, level, offsets, n)
            print("TT :: ", code, level, offsets)

#Function Call
params = ["abcdef", "xyz", "-/", "98765"]
print_taxi_serial_numbers(params, "", 0, len(params)*[0], 10)

我在重置参数方面犯了一些错误。

Answer 1

你真的不需要递归，也不需要带一堆参数。只需使用笛卡儿产品(其中有实用程序)：

from itertools import product

def print_taxi_serial_numbers(params):
    for p in product(*params):
        print(''.join(p))

>>> print_taxi_serial_numbers(["abcdef", "xyz", "-/", "98765"])
ax-9
ax-8
ax-7
ax-6
ax-5
# ...

如果你下地狱般的决心自己去做，你仍然可以保持简单：

def taxi_serial_numbers(params):
    if not params:
        return [""]
    result = []
    first, *params = params
    for char in first:
        for tsn in taxi_serial_numbers(params):
            result.append(char + tsn)
    return result

>>> taxi_serial_numbers(["abcdef", "xyz", "-/", "98765"])
['ax-9', 'ax-8', 'ax-7', 'ax-6', 'ax-5', 'ax/9', 'ax/8', ... ]

注意，当函数返回有意义的内容时，递归要容易得多，而不是只产生副作用(比如控制台打印)。您仍然可以使用函数返回值获取打印显示：

for tsn in print_taxi_serial_numbers(params):
    print(tsn)