带回文的递归

Question

我用python编写了一个递归语句

声明

回文

A palindrome is a word which reads the same backwards as forwards (madam, noon, radar…). Write a program which reads a string and prints all palindromes, which can be obtained by removing of some characters of the string. The resulting palindromes do not need to be English words!*

限制：

• 不要打印长度为1的回文（一个字母的回文）
• 每个回文只打印一次

我已经编写了下面的代码，它工作得非常好，但是在第二个定义的函数中，我没有使用递归，因为我不知道如何处理语句的这一部分。 如果有人能帮助我，我将非常感激

def find_subsets(seq, n):
    if n != 0:
        result = []
        subsets = find_subsets(seq, n-1)
        for subset in subsets:
            result += [subset]
            result += [[seq[n-1]] + subset]
        return result
    else:
        return [[]]
def check_palindrome(subsetsList):
    finalList = []
    for x in subsetsList:
        if x[::-1] == x and len(x)>1:
            string = " ".join(x)
            print(string)
        else:
           continue
word = input("Write string: ")
check_palindrome(find_subsets(word, len(word)))

Answer 1

实现check_palindrome递归版本的一种方法是将for循环替换为对check_palindrome的调用。但是，为了避免无限循环，您需要从列表中删除一个值并对其进行处理，从而在每次递归调用时将subsetsList缩小1。最后，您需要检查subsetsList何时变为空，并在此时退出递归

例如：

def check_palindrome(subsetsList):
    if not subsetsList:
        return
    
    x = subsetsList.pop()
    if x[::-1] == x and len(x)>1:
        string = " ".join(x)
        print(string)
    
    check_palindrome(subsetsList)