LeetCode(Medium)-647、Palindromic Substrings

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:
The input string length won’t exceed 1000.
題目：
給定一個字符串，統計該字符串的迴文子字符串數。
例1：
輸入：“abc”
輸出：3
說明：三個迴文字符串：“a”，“b”，“c”。
例2：
輸入：“aaa”
輸出：6
說明：六個迴文字符串：“a”，“a”，“a”，“aa”，“aa”，“aaa”。
注意：輸入字符串長度不會超過1000。

解法一：

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

Runtime: 6 ms