# 647. Palindromic Substrings

## Medium

***

Given a string `s`, return _the number of **palindromic substrings** in it_.

A string is a **palindrome** when it reads the same backward as forward.

A **substring** is a contiguous sequence of characters within the string.

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**Example 1:**

```
Input: s = "abc"
Output: 3
Explanation: Three palindromic strings: "a", "b", "c".
```

**Example 2:**

```
Input: s = "aaa"
Output: 6
Explanation: Six palindromic strings: "a", "a", "a", "aa", "aa", "aaa".
```

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**Constraints:**

* `1 <= s.length <= 1000`
* `s` consists of lowercase English letters.
