<p>Given an integer <code>n</code>, return <em>the least number of perfect square numbers that sum to</em> <code>n</code>.</p>

<p>A <strong>perfect square</strong> is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, <code>1</code>, <code>4</code>, <code>9</code>, and <code>16</code> are perfect squares while <code>3</code> and <code>11</code> are not.</p>

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

<pre>
<strong>Input:</strong> n = 12
<strong>Output:</strong> 3
<strong>Explanation:</strong> 12 = 4 + 4 + 4.
</pre>

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

<pre>
<strong>Input:</strong> n = 13
<strong>Output:</strong> 2
<strong>Explanation:</strong> 13 = 4 + 9.
</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 10<sup>4</sup></code></li>
</ul>

class Solution {
public:
    int numSquares(int n) {
        int steps = 0;
        queue<int> q;
        q.push(n);
        unordered_set<int> vis;
        
        while(! q.empty()){
            int size = q.size();
            while(size--){
                int front = q.front();
                q.pop();
                
                if(front == 0) return steps;
                if(vis.find(front) != vis.end()) continue;
                vis.insert(front);
                
                for(int i=1; i*i<=front; i++){
                    q.push(front - i*i);
                }
                
                
            }
            steps++;
        }
        
        return steps;
    }
};
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