111. Minimum Depth of Binary Tree

class Solution:
    def minDepth(self, root: Optional[TreeNode]) -> int:
        

        def dfs(node):
            if not node:
                return 0

            left = dfs(node.left)
            right = dfs(node.right)

            if not left and not right:
                return 1

            if left and right:
                return min(left, right) + 1

            if left:
                return left +  1
        
            return right + 1


        return dfs(root)

class Solution(object):
    def minDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root:
            return 0
        
        return self.iterative_level([root], 1)
        
    
    def iterative_level(self, nodes, i):
        next_level = []
        for node in nodes:
            if not node.left and not node.right:
                return i
            if node.left:
                next_level.append(node.left)
            if node.right:
                next_level.append(node.right)
        
        return self.iterative_level(next_level, i+1)