LeetCode647 Palindromic SubStrings（回文子串）

题目

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. 

方法

Manacher法

• 时间复杂度：O(n)
• 空间复杂度：O(n)

class Solution {
    public int countSubstrings(String s) {
        String s1 = preProcess(s);
        int length = s1.length();
        int c=0,maxR=0,ans=0;
        int[] p = new int[length];
        for(int i=1;i=0&&right

原文：https://www.cnblogs.com/ermiao-zy/p/15343426.html