LeetCode in Kotlin

104. Maximum Depth of Binary Tree

Easy

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

Constraints:

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

Solution

import com_github_leetcode.TreeNode
import kotlin.math.max

/*
 * 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 findDepth(root, 0)
    }

    private fun findDepth(node: TreeNode?, currentDepth: Int): Int {
        var localCurrentDepth = currentDepth
        if (node == null) {
            return 0
        }
        localCurrentDepth++
        return 1 + max(findDepth(node.left, localCurrentDepth), findDepth(node.right, localCurrentDepth))
    }
}

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