leetcode -- Same Tree

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.

 1 /**
 2  * Definition for binary tree
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public boolean isSameTree(TreeNode p, TreeNode q) {
12         // Start typing your Java solution below
13         // DO NOT write main() function
14         if((p == null) && (q == null)){
15             return true;
16         } else if((p != null) && (q != null)){
17             return cmp(p, q);
18         } else {
19             return false;
20         }
21         
22     }
23     
24     public boolean cmp(TreeNode p, TreeNode q){
25         if(p.val != q.val){
26             return false;
27         }
28         
29         TreeNode pl = p.left, pr = p.right;
30         TreeNode ql = q.left, qr = q.right;
31         
32         if(((pl == null) && (ql != null)) || ((pl != null) && (ql == null))){
33             return false;
34         }
35         
36         if(((pr == null) && (qr != null)) || ((pr != null) && (qr == null))){
37             return false;
38         }
39         boolean lFlag = true;
40         boolean rFlag = true;
41         if((pl != null) && (ql != null)){
42             lFlag = cmp(pl, ql);
43         }
44         if((pr != null) && (qr != null)){
45             rFlag = cmp(pr, qr);
46         }
47         return lFlag && rFlag;
48     }
49 }