[LeetCode] 623. Add One Row to Tree

간만에 문제풀어봤다.
타겟 뎁스에 맞춰서 새로운 노드를 형성해주고, 기존의 노드의 위상을 같이 추가해주면 되는 쉬운 문제다.

코드는 아래와 같다

/**
 * 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 targetDepth = 0
    func addOneRow(_ root: TreeNode?, _ val: Int, _ depth: Int) -> TreeNode? {
        self.targetDepth = depth
        if depth == 1 {
            let node = root
            let newNode = TreeNode(val, node, nil)
            return newNode
        }
        searchTree(root, val, 1)
        return root
    }

    func searchTree(_ node: TreeNode?, _ val: Int, _ nowDepth: Int) {
        if node == nil {
            return
        }
        if nowDepth + 1 == targetDepth {
            let left = node?.left
            let right = node?.right
            let newLNode = TreeNode(val, left, nil)
            let newRNode = TreeNode(val, nil, right)
            node?.left = newLNode
            node?.right = newRNode
        }
        searchTree(node?.left, val, nowDepth + 1)
        searchTree(node?.right, val, nowDepth + 1)
    }
}