Question

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.

Note: A leaf is a node with no children.

Difficulty:Easy

Category:Tree, Depth-first-Search

Analyze

This is a easy question for the tree problem. This question have these feature:

1. One root node question
2. We can use the return value to compare.

So we use the template code for the Tree Question.

There are four steps for this template:

1. Boundary conditions.
2. Deal with the root value.
3. recursive call funciton
4. compare ouput value

Post: Tree Question Summary

Solution

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
 public:
  int maxDepth(TreeNode* root) {
    if (root == nullptr) return 0;
    int l = maxDepth(root->left);
    int r = maxDepth(root->right);
    return max(l, r) + 1;
  }
};