<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) {
        queue<int> q;
        set<int> vis;
        q.push(n);
        int ans = 0;
        while (!q.empty()) {
            int s = q.size();
            for (int i = 0; i < s; i++) {
                int node = q.front(); q.pop();
                if (node == 0) return ans;
                for (int j = 1; j*j <= node; j++) {
                    if (!vis.count(node-j*j)) {
                        vis.insert(node-j*j);
                        q.push(node-j*j);
                    }
                }
            }
            ans ++;
        }   
        return 0;
    }
};
48960