:orphan:

Palindromic Substrings
======================

.. highlight:: none

Problem
-------
https://leetcode.com/problems/palindromic-substrings/

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.

 

**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".

 

**Constraints:**

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

.. highlight:: python

Pattern
-------
Two Pointers, String, Dynamic Programming

Approaches
----------

.. tab-set::

    .. tab-item:: Expand From Center

        **Code**

        .. literalinclude:: ../problems/medium/palindromic-substrings/palindromic_substrings__expand_from_center.py
            :language: python
            :lines: 10-

        **Test**

        >>> from palindromic_substrings__expand_from_center import countSubstrings
        >>> countSubstrings("abc")
        3
        >>> countSubstrings("aaa")
        6

        .. autofunction:: palindromic_substrings__expand_from_center.countSubstrings