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Maximum Depth of Binary Tree

Question:

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.

How to Solve:

This problem simply tests the knowledge of recursion.

The base case is when the current position is nullptr, then we return 0. Otherwise, we return:

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

My C++ Solution:

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