LeetCode 100: 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.

/**
 * 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) {
        if (p == null || q == null)
        {
            if (p == null && q == null)
                return true;
            else
                return false;
        }
        
        if (p.val != q.val)
            return false;
            
        return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
    }
}