My original solution looks exactly like below except that I did not have the "static" keyword for the methods. The solution was accepted but the runtime was ugly, like > 800 ms. However, after adding the "static", the runtime went down to only 48 ms... could anybody explain why? Thanks.

```
public class Solution {
private static Map<Integer, Integer> map = new HashMap<>();
public static int numSquares(int n) {
if (map.containsKey(n))
{
return map.get(n);
}
if (n == 0)
{
return 0;
}
int largestNum = (int)Math.floor(Math.sqrt(n));
int ans = Integer.MAX_VALUE;
for (int i = largestNum; i >= 1; i--)
{
ans = Math.min(ans, 1 + numSquares(n - i*i));
}
map.put(n, ans);
return ans;
}
}
```