BinaryTree_Leetcode_Maximum Depth of Binary Tree [swift]

https://leetcode.com/problems/maximum-depth-of-binary-tree/description/?envType=study-plan-v2&envId=top-100-liked

 

접근방법

1. 재귀탐색하여 하위 노드를 방문. 지나온 depth를 매개변수로 전달
2. 하위 노드가 존재하지 않으면 종료, depth와 sol을 비교하여 큰 값을 sol에 저장

정답코드

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public var val: Int
 *     public var left: TreeNode?
 *     public var right: TreeNode?
 *     public init() { self.val = 0; self.left = nil; self.right = nil; }
 *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
 *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
 *         self.val = val
 *         self.left = left
 *         self.right = right
 *     }
 * }
 */
class Solution {
    var sol = 0
    func maxDepth(_ root: TreeNode?) -> Int {
        guard let root else { return sol }

        func traversal(next node: TreeNode, currentDepth: Int) {
            var depth = currentDepth + 1
            if node.left == nil && node.right == nil {
                sol = max(depth, sol)
            }

            if let left = node.left {
                traversal(next: left, currentDepth: depth)
            }

            if let right = node.right {
                traversal(next: right, currentDepth: depth)
            }

        }
        traversal(next: root, currentDepth: 0)

        return sol
    }
}