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.

程式碼如下：

#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <string>
#include <climits>
#include <algorithm>
#include <sstream>
#include <functional>
#include <bitset>
 

#include <numeric>
#include <cmath>
#include <regex>

using namespace std;


class Solution 
{
public:
    int countSubstrings(string s) 
    {
        int n = s.length();
        vector<vector<bool>> dp(n, vector<bool>(n));
        for(int i = 0; i < n; i++)
        {
            for
 
 (int j = 0; j < n; j++)
            {
                if (i >= j)
                    dp[i][j] = true;
                else
                    dp[i][j] = false;
            }
        }

        int count = 0;
        for (int len = 1; len <= n; len++)
        {
            for (int i = 0; i + len < n; i++)
            {
                int j = i + len;
                if (s[i] == s[j])
                    dp[i][j] = dp[i + 1][j - 1];
                else
                    dp[i][j] = false;
            }
        }

        for (int i = 0; i < n; i++)
        {
            for (int j = i; j < n; j++)
            {
                if (dp[i][j] == true)
                    count++;
            }
        }
        return count;
    }
};