Same Tree

题目：

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.

比较两个二叉树是否相同，简单一些的就可以使用递归，如果对性能有要求的话，可以使用迭代。下面是实际代码，

递归：

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if(p == null && q == null)
return true;
if(p != null && q != null){
if(p.val != q.val)
return false;
return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
}
else
return false;
}
}