## Thursday, July 27, 2017

### [Leetcode] Palindromic Substrings, Solution

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.

[Thoughts]

[Code]
``````1:    int countSubstrings(string s) {
2:      if(s == "") return 0;
3:
4:      int count = 1;
5:      for(int i =1; i< s.size(); i++) {
6:        // palindrom length is odd and i in the middle
7:        count += countPalindrom(s, i, i);
8:
9:        // palindrom length is even and (i-1, i) in themiddle
10:        count += countPalindrom(s, i-1, i);
11:      }
12:      return count;
13:    }
14:
15:    int countPalindrom(string& s, int start, int end) {
16:      int count = 0;
17:      for(int i =0; start >=0 && end <s.size(); i++)
18:      {
19:        if(s[start] != s[end]) break;
20:
21:        count++;
22:        start--;
23:        end++;
24:      }
25:
26:      return count;
27:    }
``````