[python]Leetcode 647. Palindromic Substrings Medium

题目描述

Given a string, your task is to count how many palindromic substrings in this string.

The substrings with different start indexes or end indexes are counted as different substrings even they consist of same characters.

Example 1:

Input: “abc”
Output: 3
Explanation: Three palindromic strings: “a”, “b”, “c”.

Example 2:

Input: “aaa”
Output: 6
Explanation: Six palindromic strings: “a”, “a”, “a”, “aa”, “aa”, “aaa”.

代码实现

class Solution:
    def countSubstrings(self, s: 'str') -> 'int':
        count = 0
        for i in range(len(s)):
            count+=self.counthuiwen(s,i,i)
            count+=self.counthuiwen(s,i,i+1)
        return count
    
    def counthuiwen(self,s,i,j):
        cnt = 0
        while i>=0 and j<len(s) and s[i]==s[j]:
            cnt+=1
            i-=1
            j+=1
        return cnt