二叉树深度

最新推荐文章于 2025-01-25 23:20:32 发布

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#二叉树深度

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博客围绕二叉树最大深度展开，指出最大深度是从根节点到最远叶子节点最长路径上的节点数，给出示例二叉树 [3,9,20,null,null,15,7] 其深度为 3，还提及迭代方法求解及要多学习。

Maximum Depth of Binary Tree
Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

return its depth = 3.

我的罗里吧嗦，一点也不pythonic的解法

class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        return self.findDepth(root)
        
    def findDepth(self,root):
        if root==None:
            return 0
        if root.left==None and root.right==None:
            return 1
        elif root.left!=None and root.right!=None:
            return max(self.findDepth(root.left),self.findDepth(root.right))+1
        elif root.right!=None and root.left==None:
            return self.findDepth(root.right)+1
        elif root.left!=None and root.right==None:
            return self.findDepth(root.left)+1

下面才是python！！！

def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root:
            return 0
        left = self.maxDepth(root.left)+1
        right = self.maxDepth(root.right)+1
        return max(left, right)

还是要多多学习鸭

迭代方法：

class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        if root is None:
            return 0
        currentQueue=[root]
        ret = 0
        while currentQueue:
            nextQueue=[]
            for node in currentQueue:
                if node.left:
                    nextQueue.append(node.left)
                if node.right:
                    nextQueue.append(node.right)
            ret = ret+1
            currentQueue=nextQueue
        return ret