Same Tree

/** * 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 (q == null && p == null) {            return true;        } else 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;        }    }}