LeetCode - Maximum Depth of Binary Tree

Maximum Depth of Binary Tree

2014.1.7 23:26

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.

Solution:

　　depth(tree)  = max(depth(left subtree), depth(right subtree)) + 1;

　　depth(nullptr) = 0;

　　Time complexity is O(n), where n is the number of nodes in the tree. Space complexity is O(1).

Accepted code:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode *root) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(root == NULL){
            return 0;
        }else{
            return 1 + mymax(maxDepth(root->left), maxDepth(root->right));
        }
    }
private:
    const int &mymax(const int &a, const int &b) {
        return (a > b ? a : b);
    }
};