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.

 

思路：刚刚学习了二叉树，想到可能要分别遍历再比较，但对此题具体的实现还没有经验和具体代码结构。

参考代码：

/* https://leetcode.com/problems/same-tree/#100 Same TreeLevel: easyGiven 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.Inspired by [@JohnWeiGitHub](https://leetcode.com/discuss/3470/seeking-for-better-solution) and [@scott](https://leetcode.com/discuss/22197/my-non-recursive-method)*/import Foundationclass Easy_100_Same_Tree {    class Node {        var left: Node?        var right: Node?        var value: Int        init(value: Int, left: Node?, right: Node?) {            self.value = value            self.left = left            self.right = right        }    }    // t = O(N), average s = O(logN), worst s = O(N)    private class func isSameTree_recursion(p p: Node?, q: Node?) -> Bool {        if p == nil || q == nil {            return (p == nil && q == nil)        } else {            return p!.value == q!.value && isSameTree(p: p?.left, q: q?.left) && isSameTree(p: p?.right, q: q?.right)        }    }    // t = O(N), average s = O(logN), worst s = O(N)    private class func isSameTree_iteration(p p: Node?, q: Node?) -> Bool {        if p == nil || q == nil {            return (p == nil && q == nil)        }        var stack_p: [Node] = []        var stack_q: [Node] = []        stack_p.append(p!)        stack_q.append(q!)        while stack_p.isEmpty == false && stack_q.isEmpty == false {            let tmp_p: Node = stack_p.removeLast()            let tmp_q: Node = stack_q.removeLast()            if tmp_p.value != tmp_q.value {                return false            }            if tmp_p.left != nil {                stack_p.append(tmp_p.left!)            }            if tmp_q.left != nil {                stack_q.append(tmp_q.left!)            }            if stack_p.count != stack_q.count {                return false            }            if tmp_p.right != nil {                stack_p.append(tmp_p.right!)            }            if tmp_q.right != nil {                stack_q.append(tmp_q.right!)            }            if stack_p.count != stack_q.count {                return false            }        }        return stack_q.count == stack_q.count    }    class func isSameTree(p p: Node?, q: Node?) -> Bool {        return isSameTree_iteration(p: p, q: q)    }}

总结：时间原因，代码还未全部搞懂，树的初始化也有所不同，leetcode上还没AC，空时再回头看这题。