minimum-depth-of-binary-tree.py

# -*- coding:utf-8 -*-


# 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.
#
# Note: A leaf is a node with no children.
#
# Example:
#
# Given binary tree [3,9,20,null,null,15,7],
#
#
#     3
#    / \
#   9  20
#     /  \
#    15   7
#
# return its minimum depth = 2.
#


# Definition for a binary tree 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 root == None:
            return 0
        if root.left==None or root.right==None:
            return self.minDepth(root.left)+self.minDepth(root.right)+1
        return min(self.minDepth(root.right),self.minDepth(root.left))+1