Lintcode 837. Palindromic Substrings (Easy) (Python)

2Young2Simple

于 2018-07-28 16:11:05 发布

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文章标签： Lintcode Python

本文链接：https://blog.youkuaiyun.com/weixin_41677877/article/details/81262136

本文介绍了一种算法，用于计算给定字符串中所有回文子串的数量。通过逐字符扫描并利用回文特性，该算法能高效地解决此问题。

Palindromic Substrings

Description:

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

Code:

class Solution:
    """
    @param str: s string
    @return: return an integer, denote the number of the palindromic substrings
    """
    def countPalindromicSubstrings(self, str):
        # write your code here
        cnt = 0
        ls = len(str)
        for i in range(ls):
            cnt += 1

            l = i-1
            r = i+1
            if l>=0 and r<ls and str[l]==str[r]:
                cnt += 1
                l -= 1
                r += 1

            l = i-1
            r = i
            if l>=0 and r<ls and str[l]==str[r]:
                cnt += 1
                l -= 1
                r += 1
        return cnt