/** * Definition for a binary tree node. * public class TreeNode { *     public int val; *     public TreeNode left; *     public TreeNode right; *     public TreeNode(int x) { val = x; } * } */public class Solution {    List
     
       list1 = new List
      
       ();        List
       
         list2 = new List
        
         ();        void postTree(TreeNode tree, int type)        {            if (type == 1)            {                list1.Add(tree);            }            else            {                list2.Add(tree);            }            if (tree != null)            {                if (tree.left != null)                {                    postTree(tree.left, type);                }                else                {                    postTree(null, type);                }                if (tree.right != null)                {                    postTree(tree.right, type);                }                else                {                    postTree(null, type);                }            }        }        public bool IsSameTree(TreeNode p, TreeNode q)        {            postTree(p, 1);            postTree(q, 2);            var len1 = list1.Count;            var len2 = list2.Count;            if (len1 != len2)            {                return false;            }            else            {                for (int i = 0; i < len1; i++)                {                    if (list1[i] == null && list2[i] != null)                    {                        return false;                    }                    if (list1[i] != null && list2[i] == null)                    {                        return false;                    }                    if (list1[i] != null && list2[i] != null && list1[i].val != list2[i].val)                    {                        return false;                    }                }                return true;            }        }}