<p>Given a string <code>s</code>, return <em>the number of <strong>palindromic substrings</strong> in it</em>.</p>

<p>A string is a <strong>palindrome</strong> when it reads the same backward as forward.</p>

<p>A <strong>substring</strong> is a contiguous sequence of characters within the string.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;abc&quot;
<strong>Output:</strong> 3
<strong>Explanation:</strong> Three palindromic strings: &quot;a&quot;, &quot;b&quot;, &quot;c&quot;.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;aaa&quot;
<strong>Output:</strong> 6
<strong>Explanation:</strong> Six palindromic strings: &quot;a&quot;, &quot;a&quot;, &quot;a&quot;, &quot;aa&quot;, &quot;aa&quot;, &quot;aaa&quot;.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s</code> consists of lowercase English letters.</li>
</ul>

class Solution {
public:
    unordered_set<string> palindromes;
    int count = 0;

    void expandFromCenter(string &s, int left, int right) {
        // in-bounds ans the palidrome check
        while (left>=0 && right<s.length() && s[left] == s[right]) {
            left--;
            right++;
            palindromes.insert(s.substr(left+1, right-left-1));
            count++;
        }
    }
    int countSubstrings(string s) {
        for (int i=0; i<s.length(); i++) {
            // odd length palindrome
            expandFromCenter(s, i, i);
            // even length palindrome
            expandFromCenter(s, i, i+1);
        }

        return count;
    }
};
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