CODE

/**
* Definition for a binary tree node.
* public class TreeNode {
*     public int val;
*     public TreeNode left;
*     public TreeNode right;
*     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
*         this.val = val;
*         this.left = left;
*         this.right = right;
*     }
* }
*/

public class Solution {
  bool same = true;

  public bool IsSameTree(TreeNode p, TreeNode q) {

    if (p == null && q != null)
    {
      same = false;
      return same;
    }
    if (q == null && p != null)
    {
      same = false;
      return same;
    }
    if (p == null && q == null)
    {
      return same;
    }
    
    if (p.val != q.val)
    {
      same = false;
      return same;
    }

    IsSameTree(p.left, q.left);
    IsSameTree(p.right, q.right);
    
    return same;
  }
}