new_contents: """
  Given a binary tree, find its minimum depth.
  The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
  """
  
  class TreeNode(object):
      def __init__(self, x):
           self.val = x
           self.left = None
           self.right = None
  
  
  class Solution(object):
      def minDepth(self, root):
          """
          :type root: TreeNode
          :rtype: int
          """
          if not root:
              return 0
          if not root.left and not root.right:
              return 1
          if not root.left:
              return self.minDepth(root.right)+1
          if not root.right:
              return self.minDepth(root.left)+1
  
          min_left = self.minDepth(root.left)
          min_right = self.minDepth(root.right)
          min_depth = min(min_left,min_right) + 1
          return min_depth
  
subject: Create MinimumDepthBinaryTree.py