Same Tree

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
   public boolean isSameTree(TreeNode p, TreeNode q) {
        //special case1
        if (p == null && q == null)
            return true;
        //if just one of the node is null, return false
        if (p == null || q == null)
            return false;
        return (p.val == q.val) && isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
    }
}