104. maximum depth of binary tree

Method 1 ：dfs

class Solution {
    
public:
    int maxDepth(TreeNode* root) {
    
        if (root == nullptr) return 0;
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
};

 author ：LeetCode-Solution
 link ：https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/solution/er-cha-shu-de-zui-da-shen-du-by-leetcode-solution/
 source ： Power button （LeetCode）
 The copyright belongs to the author . Commercial reprint please contact the author for authorization , Non-commercial reprint please indicate the source .

Method 2 ：bfs

Using the queue

class Solution {
    
public:
    int maxDepth(TreeNode* root) {
    
        if (root == nullptr) return 0;
        queue<TreeNode*> Q;
        Q.push(root);
        int ans = 0;
        while (!Q.empty()) {
    
            int sz = Q.size();
            while (sz > 0) {
    
                TreeNode* node = Q.front();Q.pop();
                if (node->left) Q.push(node->left);
                if (node->right) Q.push(node->right);
                sz -= 1;
            }
            ans += 1;
        } 
        return ans;
    }
};

 author ：LeetCode-Solution
 link ：https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/solution/er-cha-shu-de-zui-da-shen-du-by-leetcode-solution/
 source ： Power button （LeetCode）
 The copyright belongs to the author . Commercial reprint please contact the author for authorization , Non-commercial reprint please indicate the source .