104. Maximum Depth of Binary Tree
我的思路:
要找一棵二叉树的最大深度,只要找它子树的最大深度+1,显然递归。
我的代码:
/**
* 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 max(1+maxDepth(root->left), 1+maxDepth(root->right));
}
};
已经是最快速度的了,最快代码给出了一种尾递归的解法:
/**
* 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 = 0;
void dfs(TreeNode* node, int depth) {
if (!node) {
maxdepth = max(maxdepth, depth);
return;
}
dfs(node->left, depth+1);
dfs(node->right, depth+1);
}
int maxDepth(TreeNode* root) {
dfs(root, 0);
return maxdepth;
}
};