LeetCode 104: Maximum Depth of Binary Tree

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">方法1：递归，返回左子树或右子树加1，然后把这个值当做下次的输入。</span>

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

方法2：遍历

class Solution {
public:
    int maxDepth(TreeNode *root)
    {
        if(root == NULL)    return 0;
        int res = 0;
        queue<TreeNode *> q;
        q.push(root);
        while(!q.empty())
        {
            ++ res;
            for(int i = 0, n = q.size(); i < n; ++ i)
            {
                TreeNode *p = q.front();
                q.pop();
                if(p -> left != NULL)   q.push(p -> left);
                if(p -> right != NULL)  q.push(p -> right);
            }
        }

    return res;
    }
};