title: What's the runtime complexity of this code which contains four recursive calls?
body: <p>what's its run-time complexity which has 4 recursive functions.</p>
  
  <pre><code>def func(arr,i,j,N):
  
    if i==N or j==N or i&lt;0 or j&lt;0: 
       return
    if arr[i][j]==1 or arr[i][j]=='X': 
       return
  
    arr[i][j]='X' 
  
    func(arr,i,j+1,N) 
    func(arr,i,j-1,N) 
    func(arr,i+1,j,N) 
    func(arr,i-1,j,N) 
  
    return(arr)
  </code></pre>