Q:
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.
A:
/** * 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) { if(!root) return 0; return 1+ max(maxDepth(root->left), maxDepth(root->right)); } };
Learned:
注意,以前的一个错误。 就是,null也可以作为参数传递给方法。
也就是说,上面的代码, 当root.left == null 的时候,依然正确。
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