Prints a path from root node to a specified node in a tree

PrintPathFromRootToNode.swift

import Foundation

class TreeNode {
  var data: Int
  var left: TreeNode?
  var right: TreeNode?

  init(data: Int) {
    self.data = data
  }
}

class BinaryTree {
  var root: TreeNode

  init(root: TreeNode) {
    self.root = root
  }

  func printPathFromRoot(to node: TreeNode) -> [Int] {
    pathFromRoot(to: node).compactMap { $0.data }
  }

  func pathFromRoot(to node: TreeNode) -> [TreeNode] {
    if root.left == nil, root.right == nil {
      return [root]
    }
    
    return path(from: root, to: node)
  }

  func path(from node1: TreeNode, to node2: TreeNode) -> [TreeNode] {
    if node1.left?.data == node2.data || node1.right?.data == node2.data {
      return [node1, node2]
    }

    if let left = node1.left {
      let leftPath = path(from: left, to: node2)
      if !leftPath.isEmpty {
        return [node1] + leftPath
      }
    }
    
    if let right = node1.right {
      let rightPath = path(from: right, to: node2)
      if !rightPath.isEmpty {
        return [node1] + rightPath
      }
    }
    
    return []
  }
}

let node20 = TreeNode(data: 20)
let node8 = TreeNode(data: 8)
let node22 = TreeNode(data: 22)
let node5 = TreeNode(data: 5)
let node3 = TreeNode(data: 3)
let node25 = TreeNode(data: 25)
let node10 = TreeNode(data: 10)
let node14 = TreeNode(data: 14)

node20.left = node8
node20.right = node22
node22.right = node25
node8.left = node5
node8.right = node3
node3.left = node10
node3.right = node14

let tree = BinaryTree(root: node20)
print("path to node: \(tree.printPathFromRoot(to: node14))")