Palindromic Substrings

Similar Problems:

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".

Note:

The input string length won’t exceed 1000.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## https://code.dennyzhang.com/palindromic-substrings ## Basic Ideas: Choose each character as the central letter ## The palindrome may have odd length and even length. ## Complexity: Time O(n^2), Space O(1) class Solution: def countSubstrings(self, s): """ :type s: str :rtype: int """ length = len(s) res = length for i in range(length): for (l,r) in [(i-1, i+1), (i, i+1)]: while l >=0 and r <= length-1 and s[l] == s[r]: res += 1 l, r = l-1, r+1 return res