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],
3
/ 9 20
/ 15 7
return its depth = 3.
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求二叉树的最大深度。
emmm，用bfs时，注意要用循环，要先遍历完一层，再遍历下一层。和leetcode111 Minimum Depth of Binary Tree几乎相似，只是少写了一行代码而已。
/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: int maxDepth(TreeNode* root) { queue<TreeNode*> q; if(!root) return 0; q.push(root); int res = 0; while(!q.empty()){ res++; for(int i = q.size(); i > 0; i--){ //必须写循环，否则在[3,9,20,null,null,15,7]时，会返回5。嗯，就是返回了二叉树的结点的个数。 auto t = q.front(); q.pop(); if(t->left) q.push(t->left); if(t->right) q.push(t->right); } } return res; } };
C++代码：
(二叉树 bfs) leetcode 104. Maximum Depth of Binary Tree
原文：https://www.cnblogs.com/Weixu-Liu/p/10714904.html