Same Tree

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.
题意：
题目：相同树，
给定两个二叉树，写一个函数检测它们是否相同。
只有当结构一致和结点的值一致的时候，才能认为这两个二叉树相同。