[Convert Binary tree input in AlgoExpert to tree input value]

ConvertToBinaryTreeSuitableForInput.swift

class Program {
    class BST {
        var value: Int
        var left: BST?
        var right: BST?

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

// Converter
let treeJson =
"""
{
  "nodes": [
    {"id": "1", "left": "2", "right": "3", "value": 1},
    {"id": "2", "left": "4", "right": "5", "value": 2},
    {"id": "3", "left": "6", "right": "7", "value": 3},
    {"id": "4", "left": "8", "right": "9", "value": 4},
    {"id": "5", "left": "10", "right": null, "value": 5},
    {"id": "6", "left": null, "right": null, "value": 6},
    {"id": "7", "left": null, "right": null, "value": 7},
    {"id": "8", "left": null, "right": null, "value": 8},
    {"id": "9", "left": null, "right": null, "value": 9},
    {"id": "10", "left": null, "right": null, "value": 10}
  ],
  "root": "1"
}
"""

let jsonData = Data(treeJson.utf8)
let decoder = JSONDecoder()
let trees = try! decoder.decode(BSTJson.self, from: jsonData)
var inputHash = [String: Program.BST]()
trees.nodes.forEach {
    inputHash[$0.id] = Program.BST(value: $0.value)
}
inputHash.forEach { input in
    guard let node = trees.nodes.first(where: { $0.value == input.value.value }) else { return }
    if let right = node.right {
        input.value.right = inputHash[right]
    }

    if let left = node.left {
        input.value.left = inputHash[left]
    }
}

let input = inputHash.values.first(where: { Int(trees.root)  == $0.value})!