// MARK: - Найти одинаковые поддеревья
// 625

func findDuplicateSubtrees(_ root: TreeNode?) -> [TreeNode?] {
    var hashMap = [Int: Bool]()
    var result = [TreeNode?]()

    func dfs(_ node: TreeNode?) -> Int {
        guard let node = node else { return 0 }
        let hashValue = [node.val, dfs(node.left), dfs(node.right)].hashValue
        if hashMap[hashValue] == true {
            result.append(node)
        }
        hashMap[hashValue] = hashMap[hashValue] == nil
        return hashValue
    }

    dfs(root)
    return result
}