100_SameTree.swift

//
//  100_SameTree.swift
//  HRSwift
//
//  Created by yansong li on 2016-08-02.
//  Copyright © 2016 yansong li. All rights reserved.
//

import Foundation

/**
  Given two binary trees, write a function to check if they are equal or not.
  
  Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
 */

/**
  Swift Knowledge:
 
  Enum Comparison
 
  Algorithem Knowledge:
 
  Recursive call.
 */

/**
  100. Same Tree
  https://leetcode.com/problems/same-tree/
 */

class Solution_SameTree {
  func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool {
    switch(p, q){
      case (let .some(leftRoot), let .some(rightRoot)):
        let valEqual = (leftRoot.val == rightRoot.val)
        let leftEqual = isSameTree(leftRoot.left, rightRoot.left)
        let rightEqual = isSameTree(leftRoot.right, rightRoot.right)
        return valEqual && leftEqual && rightEqual
      case (.none, .none):
        return true
      default:
        return false
    }
  }
}