Maximum Depth of Binary Tree

Problem

Given the root of a binary tree, return its maximum depth.

A binary tree’s maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Constraints

• The number of nodes in the tree is in the range [0, 104].
• -100 <= Node.val <= 100

Solution

The problem Maximum Depth of Binary Tree can be solved recursively by comparing the maximum depth of left and right binary tree until the farthest leaf node has been reached.

Implementation

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution
{
  public:
    int maxDepth(TreeNode *root)
    {
        if (root == NULL)
            return 0;

        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }
};