Minimum Depth of a Binary Tree

# Python program to find minimum depth of a given Binary Tree 
  
# Tree node 
class Node: 
    def __init__(self , key): 
        self.data = key  
        self.left = None
        self.right = None
  
def minDepth(root): 
    # Corner Case.Should never be hit unless the code is  
    # called on root = NULL 
    if root is None: 
        return 0 
      
    # Base Case : Leaf node.This acoounts for height = 1 
    if root.left is None and root.right is None: 
        return 1
      
    # If left subtree is Null, recur for right subtree 
    if root.left is None: 
        return minDepth(root.right)+1
      
    # If right subtree is Null , recur for left subtree 
    if root.right is None: 
        return minDepth(root.left) +1 
      
    return min(minDepth(root.left), minDepth(root.right))+1
  
# Driver Program  
root = Node(1) 
root.left = Node(2) 
root.right = Node(3) 
root.left.left = Node(4) 
root.left.right = Node(5) 
print minDepth(root) 
  
# This code is contributed by Nikhil Kumar Singh(nickzuck_007)