获取奇数回文长度 [英] Get Odd Length Palindrome

问题描述

我试图找到最长的奇数回文，但是我编写的代码并没有给我完整的回文，只是其中的一部分.任何帮助都会很棒！

I'm trying to find the longest odd length palindrome, but the code I've written isn't giving me the full palindrome, just part of it. Any help would be great!

def get_odd_palindrome_at(s, index):
    ''' (str, int) -> str

    > get_odd_palindrome_at('tbababt', 3)
    'tbababt'
    > get_odd_palindrome_at('color', 2)
    'olo'
    '''

    palindrome = s[index]
    i = index

    for char in s:
        if s[i - 1] == s[i + 1]:
            palindrome = s[i - 1] + palindrome + s[i + 1]
            i = i + 1

    return palindrome

推荐答案

使i与index保持距离，并确保不要越界.最后，仅当找到i的最终值时，才构建结果字符串.每次迭代都没有用:

Make i the distance from the index and make sure not to loop out of bounds. Finally, only build the result string when you have found the final value of i. There is no use in doing it in every iteration:

def get_odd_palindrome_at(s, index):
    for i in range(1, index+1):
        if index + i >= len(s) or s[index - i] != s[index + i]:
            i -= 1
            break

    return s[index-i:index+i+1]

或者，您可以使用两个变量，从而稍微简化了代码:

Alternatively, you could use two variables, which simplifies the code a bit:

def get_odd_palindrome_at(s, index):
    i = index
    j = index
    while i >= 0 and j < len(s) and s[i] == s[j]:
        i -= 1
        j += 1

    return s[i+1:j]

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