Maximum Depth of Binary Tree

Description

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.

Example
Given a binary tree as follow:
  1
 / \ 
2   3
   / \
  4   5
The maximum depth is 3.

Link

Lintcode_ladder

Method

1. Divide and conquer, recursion, O(n)
2. BFS, level traversal

Example

1. 1

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param root: The root of binary tree.
     * @return: An integer
     */
    int maxDepth(TreeNode *root) {
        // write your code here
        // test currnt level is existed or not
        if (!root) {
            return 0;
        }
        // get max depth from left and right 
        return max(maxDepth(root->left), maxDepth(root->right))+1;
    }
};

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