min-depth-bt.py

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def minDepth(self, root: Optional[TreeNode]) -> int:
        if root is None:
            return 0
        
        #Base Case => H=1
        if root.left is None and root.right is None:
            return 1
        
        if root.left is None:
            #if left is none, go right
            return self.minDepth(root.right)+1 #1 is height of tree
        
        if root.right is None:
            return self.minDepth(root.left)+1
        
        return min(self.minDepth(root.left),self.minDepth(root.right))+1