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.
答题意思就是判断两个树是否一样。也就是数的结构和节点数值都要一样就认为两棵树一样。
代码如下：
public class Solution { public boolean isSameTree(TreeNode p, TreeNode q) { if(p==null&&q==null) return true; if(p==null||q==null) return false; if(p.val==q.val){ return isSameTree(p.left,q.left)&&isSameTree(p.right,q.right); } return false; } }
