回文递归

Question

我有一个 python 的递归语句。

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：

不打印长度为 1 的回文（单字母回文）。
每个回文恰好打印一次。

我写了下面的代码，效果很好，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这部分语句。如果有人能帮助我，我将不胜感激。

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用对 check_palindrome 的调用替换 for 循环。然而，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 何时变空并在该点退出递归。

示例：

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)

回文递归

Recursion with palindromes

python

string

recursion

substring

palindrome