zoukankan      html  css  js  c++  java
  • 647. Palindromic Substrings

    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:

    1. The input string length won't exceed 1000.

    Approach #1: Greedy. [Java]

    class Solution {
        int count = 0;
        public int countSubstrings(String s) {
            if (s == null || s.length() == 0) return 0;
            for (int i = 0; i < s.length(); ++i) {
                solve(s, i, i);
                solve(s, i, i+1);
            }
            return count;
        }
        
        public void solve(String s, int left, int right) {
            while (left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
                left--;
                right++;
                count++;
            }
        }
    }
    

      

    Analysis:

    Step1: Start a for loop to point at every single character from where we will trace the palindrome string.

    solve(s, i, i);  // To check the palindrome of odd length palindromic subsring.

    solve(s, i, i+1);   // To check the palindrome of even length palindrome substring.

    Step2: From each character of the string, we will keep checking is the substring is a palindrome and increment the palindrome count. To check the palindrome, keep checking the left and right of the character is it is same or not.

    Reference:

    https://leetcode.com/problems/palindromic-substrings/discuss/105688/Very-Simple-Java-Solution-with-Detail-Explanation

    永远渴望,大智若愚(stay hungry, stay foolish)
  • 相关阅读:
    LeetCode522. 最长特殊序列 II
    docker activiti部署到Linux环境,流程图乱码
    linux docker 命令
    linux 安装docker
    JSON,JSONOBJECT,JSONARRAY 互转
    Python和java 的区别笔记(未完成)
    程序员常读书单整理,附下载地址
    javaweb同一个项目打包两次放在同一个tomcat下
    SSM项目集成Redis
    Chrome浏览器崩溃
  • 原文地址:https://www.cnblogs.com/h-hkai/p/10511547.html
Copyright © 2011-2022 走看看