我的程序：
class Solution(object): def longestPalindrome(self, s): """ :type s: str :rtype: str """ if s==‘‘: return ‘‘ if len(s)==1: return s res=[] for i in range(len(s)): c=s[i:].count(s[i]) if c !=1: b=s[::-1].index(s[i]) j=len(s)-b-1 if s[i:j+1]==s[i:j+1][::-1] and i!=j: res.append(s[i:j+1]) else: c-=1 t=s[i:j] if len(t)==2: if t[0]==t[1]: res.append(t) break else: break b=t[::-1].index(t[0]) j=len(t)-b-1 if t[:j+1]==t[:j+1][::-1] and j!=0: res.append(t[:j+1]) c-=1 while c>1: t=s[i:i+j] if len(t)==2: if t[0]==t[1]: res.append(t) break else: break b=t[::-1].index(t[0]) j=len(t)-b-1 if t[:j+1]==t[:j+1][::-1] and j!=0: res.append(t[:j+1]) c-=1 if len(res)==0: return s[0] if len(res)==1: return res[0] m=max(len(res[i]) for i in range(len(res))) for i in range(len(res)): if len(res[i])==m: return res[i]
执行用时为 20 ms 的范例
class Solution(object):
def longestPalindrome(self, s):
"""
:type s: str
:rtype: str
"""
if len(s) < 2 or s == s[::-1]:
return s
length = 1 even_medium = 0 even_left = 0 for i in range(len(s) - 1): if i - even_left >= 0 and s[i - even_left] == s[i + 1]: substring = s[i - even_left: i + 2] if substring == substring[: : -1]: even_medium = i length = even_left + 2 even_left = even_left + 2 odd_medium = 0 half = (length + 1) // 2 odd_left = (length + 1) // 2 for j in range(half, len(s) - half): if j - odd_left >= 0 and s[j - odd_left] == s[j + half]: substring = s[j - odd_left: j + half + 1] if substring == substring[: : -1]: odd_medium = j length = odd_left + half + 1 odd_left = odd_left + 2 if length % 2 == 0: return s[even_medium + 2 - length: even_medium + 2] else: if length == 1: return s[0] else: return s[odd_medium + half + 1 - length: odd_medium + half + 1]
分析改进：
将我的程序里面的
if s==‘‘: return ‘‘ if len(s)==1: return s
换成：
if len(s) < 2 or s == s[::-1]: return s
其他的还没仔细看。。。。
——2019.10.11
原文：https://www.cnblogs.com/taoyuxin/p/11653794.html