LeetCode ---- 111. Minimum Depth of Binary Tree解题报告

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.

 

# -*- coding:utf-8 -*-
__author__ = 'yangxin_ryan'
"""
Solutions:
求二叉树的最小深度
我们可以先列举所有情况：
1.当节点为叶子结点，深度为1
2.当根节点为None,深度为0
3.当节点只有左孩子（或右孩子）时，深度为左孩子（右孩子）+ 1
4.当节点既有左孩子又有右孩子时，深度为min(左孩子，右孩子) + 1
5.递归上面的情况
""&#