字符串的打印功率集 [英] print powerset of a string

问题描述

我正在尝试编写python代码以打印字符串的 powerset ，但是遇到了一些错误.这就是我所拥有的:

I'm trying to write python code to print the powerset of a string, but am running into some bugs. Here's what I've got:

def getperm (string):
    perm = []
    if len(string) == 0:
        perm.append("")
        return perm
    #if len(string) == 1:
    #   perm.append(string)
    #   perm.append("")
    first = string[0]
    print "first = " + str(first)
    rem = string[1:len(string)]
    print "rem = " + str(rem)
    words = getperm(rem)
    for word in words:
        for i in range(len(word)):
            temp = string[0:i] + first + string[i:len(string)]
            print "temp = " + str(temp)
            perm.append(temp)

    return perm

if __name__=="__main__":
    a = "ab"
    mag  = getperm(a)
    print mag

我的预期输出将是:

['', 'a', 'b', 'ab']

我的实际输出是:

[]

有人可以帮我弄清楚发生了什么吗?这是python的细微差别吗，还是我的代码中存在错误?我认为我的代码应该没问题-我即将结束《破解编码面试》的第五版

Can anyone help me figure out what's going on? Is this some nuance of python, or is there a bug in my code? I think my code should be ok -- I'm going off the fifth edition of Cracking the coding interview

谢谢！

推荐答案

您想得太多

这部分正在尝试做很多事情

This part is trying to do too much

for word in words:
    for i in range(len(word)):
        temp = string[0:i] + first + string[i:len(string)]
        print "temp = " + str(temp)
        perm.append(temp)

看看它到底应该是多么简单

See how simple it really should be

def get_powerset (string):
    perm = []
    if len(string) == 0:
        perm.append("")
        return perm
    #if len(string) == 1:
    #   perm.append(string)
    #   perm.append("")
    first = string[0]
    print "first = " + str(first)
    rem = string[1:len(string)]
    print "rem = " + str(rem)
    words = get_powerset(rem)
    perm.extend(words)
    for word in words:
        perm.append(first+word)

    return perm

if __name__=="__main__":
    a = "ab"
    mag  = get_powerset(a)
    print mag

现在您应该可以通过少量重构使代码看起来更好

Now you should be able to make the code look a lot nicer with a little refactoring

这篇关于字符串的打印功率集的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！