[LeetCode] 647. Palindromic Substrings

 轉自LeetCode

Given a string s, return the number of palindromic substrings in it.

A string is a palindrome when it reads the same backward as forward.

A substring is a contiguous sequence of characters within the string.

 

Example 1:

Input: s = "abc"
Output: 3
Explanation: Three palindromic strings: "a", "b", "c".

Example 2:

Input: s = "aaa"
Output: 6
Explanation: Six palindromic strings: "a", "a", "a", "aa", "aa", "aaa".

 

Constraints:

• 1 <= s.length <= 1000
• s consists of lowercase English letters.

Solution

可以沿用 longest palindromic substring 的概念

用 dp[i][j] 來表示 s[i] 到 s[j] 是否是一個回文串

如果是，就把 counter + 1

code 如下

Kotlin