<pre class="shiki github-dark shaku"><code>/** * @param {string} str * @return {number} */function countPalindromicSubstr(str) { // your code here let output = 0 function helper(string, left, right) { while (left &gt;= 0 &amp;&amp; right &lt;= string.length &amp;&amp; string[left] === string[right]) { output += 1 left-- right++ } } for (let i = 0; i &lt; str.length; i++) { helper(str, i, i) helper(str, i, i + 1) } return output}</code></pre>

O(n2)

A palindromic string reads the same backward as forward, such as 'madam'. Now given a string, count how many substrings it has? Like 'madam', it has f…