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.

思路：

递归

package tree;public class SameTree {    public boolean isSameTree(TreeNode p, TreeNode q) {        if (p == null && q == null) return true;        if (p == null || q == null) return false;        return p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right);    }        public static void main(String[] args) {        // TODO Auto-generated method stub    }}