/**
 * 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 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 (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));
    }
}
