<p>It is a sweltering summer day, and a boy wants to buy some ice cream bars.</p>
<p>At the store, there are <code>n</code> ice cream bars. You are given an array <code>costs</code> of length <code>n</code>, where <code>costs[i]</code> is the price of the <code>i<sup>th</sup></code> ice cream bar in coins. The boy initially has <code>coins</code> coins to spend, and he wants to buy as many ice cream bars as possible. </p>
<p><strong>Note:</strong> The boy can buy the ice cream bars in any order.</p>
<p>Return <em>the <strong>maximum</strong> number of ice cream bars the boy can buy with </em><code>coins</code><em> coins.</em></p>
<p>You must solve the problem by counting sort.</p>