[LeetCode] 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.

找出字符串中的所有回文子串。

1、首先判断回文

2、利用substr将字符串分割后，进行判断统计

class Solution {
public:
    int countSubstrings(string s) {
        int res = 0;
        for (int i = 0; i < s.size(); i++) {
            for (int j = 1; j <= s.size() - i; j++) {
                if (isPalindromic(s.substr(i, j)))
                    res++;
            }
        }
        return res;
    }
    bool isPalindromic(string str) {
        int lo = 0, hi = str.size() - 1;
        while (lo < hi) {
            if (str[lo] != str[hi]) {
                return false;
            }
            else {
                lo++;
                hi--;
            }
        }
        return true;
    }
};
// 204 ms