(LeetCode) 104. Maximum Depth of Binary Tree

Maximum Depth of Binary Tree

• Explore : Interview > Top Interveiw Questions > Easy Collection
• 분류 : Trees
• 난이도 : Easy

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.

Example 1

Input: root = [3,9,20,null,null,15,7]
Output: 3

Example 2

Input: root = [1,null,2]
Output: 2

Example 3

Input: root = []
Output: 0

Example 4

Input: root = [0]
Output: 1

Constraints

• The number of nodes in the tree is in the range [0, 10^4].
• -100 <= Node.val <= 100

Solution

Exapnder

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {
    fun maxDepth(root: TreeNode?): Int {
        return if (root == null) {
            0
        } else {
            Math.max(maxDepth(root.left), maxDepth(root.right)) + 1
        }
    }
}

Point of Thinking

• DFS 문제이므로 재귀함수로 처리하면 간단하게 해결할 수 있다.