Leetcode: Minimum Depth of Binary Tree

Question

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.

Hide Tags Tree Depth-first Search

Analysis

This problem is slightly different from the problem “maximum depth of binary tree”. If left child of subroot is None, the minimum depth of this subroot is not 0 because we should keep searching the right node.

Solution

[code]# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    # @param {TreeNode} root
    # @return {integer}
    def minDepth(self, root):
        return self.search(root)

    def search(self,subroot):
        if subroot==None:
            return 0

        if subroot.left==None:
            return self.search(subroot.right)+1

        if subroot.right==None:
            return self.search(subroot.left)+1

        return 1+min(self.search(subroot.left), self.search(subroot.right))