104. Maximum Depth of Binary Tree

Problem

Difficulty: Easy
Tags: Tree, Depth-First Search, Breadth-First Search, Binary Tree

Intuition

This one was seems much eaisier than the symmetric tree question. Also, it actually was. it was easy to think the reculsive mechanism to understand the depth of a tree.

Approach

I used the reculsive method to solve the problem. Firstly, I found the base case, where the the null tree has zero depth, and the depth of a tree is its deepest child’s depth plus one. and it was easy to use that knowledge and convert it into code.

Solution

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
int maxDepth(struct TreeNode* root) {
    if(!root){
        return 0;
    }
    else{
        int tmpleft,tmpright;
        tmpleft = maxDepth(root->left);
        tmpright = maxDepth(root->right);
        return tmpleft > tmpright ? tmpleft+1 : tmpright+1;
    }
}

Complexity

it calls maxDepth() function for each node of the tree.

Time: $O(n)$ where n is # of Nodes of the root tree.
Space: $O(n)$ where n is # of Nodes of the root tree.

Thoughts

It was easy and it took less than 3 minuites to solve. I probably need more challenging problem that takes like 50 minuites to solve and write about the solution about 10 minuites. it was Great!! XD