C++ 二叉查找树编码与解码

给定一个二叉查找树，实现对该二叉查找树编码与解码功能。编码即将该二叉树转为字符串，解码即将字符串转为二叉查找树。不限制使用何种编码算法，只需保证当对二叉查找树调用编码功能后可再调用解码功能将其复原。

#include <stdio.h>
#include <string>
#include <vector>
struct TreeNode
{
 int val;
 TreeNode* left;
 TreeNode* right;
 TreeNode(int x) : val(x), left(NULL), right(NULL) {};
};
void preorder(TreeNode* node, int layer)
{
 if (!node)
 {
  return;
 }
 for (int i = 0; i < layer; i++)
 {
  printf("-----");
 }
 printf("[%d]\n", node->val);
 preorder(node->left, layer + 1);
 preorder(node->right, layer + 1);
}
class Codec
{
public:
 Codec(){}
 ~Codec(){}
 std::string serialize(TreeNode* root)
 {
  std::string data;
  BST_preorder(root, data);
  return data;
 }
 TreeNode* deserialize(std::string data)
 {
  if (data.length()==0)
  {
   return NULL;
  }
  std::vector<TreeNode*> node_vec;
  int val = 0;
  for (int i = 0; i < data.length(); i++)
  {
   if (data[i]=='#')
   {
    node_vec.push_back(new TreeNode(val));
    val = 0;
   }
   else
   {
    val = val * 10 + data[i] - '0';
   }
  }
  for (int i = 1; i < node_vec.size(); i++)
  {
   BST_insert(node_vec[0], node_vec[i]);
  }
  return node_vec[0];
 }
private:
 void change_int_to_string(int val, std::string& str_val)
 {
  std::string tmp;
  while (val)
  {
   tmp += val % 10 + '0';
   val = val / 10;
  }
  for (int i = tmp.length() - 1; i >= 0; i--)
  {
   str_val += tmp[i];
  }
  str_val += '#';
 }
 void BST_preorder(TreeNode* node, std::string& data)
 {
  if (!node)
  {
   return;
  }
  std::string str_val;
  change_int_to_string(node->val, str_val);
  data += str_val;
  BST_preorder(node->left, data);
  BST_preorder(node->right, data);
 }
 void BST_insert(TreeNode* node, TreeNode* insert_node)
 {
  if (insert_node->val < node->val)
  {
   if (node->left)
   {
    BST_insert(node->left, insert_node);
   }
   else
   {
    node->left = insert_node;
   }
  }
  else
  {
   if (node->right)
   {
    BST_insert(node->right, insert_node);
   }
   else
   {
    node->right = insert_node;
   }
  }
 }
};
int main()
{
 TreeNode a(8);
 TreeNode b(3);
 TreeNode c(10);
 TreeNode d(1);
 TreeNode e(6);
 TreeNode f(15);
 a.left = &b;
 a.right = &c;
 b.left = &d;
 b.right = &e;
 c.right = &f;
 Codec solve;
 std::string data = solve.serialize(&a);
 printf("%s\n", data.c_str());
 TreeNode* root = solve.deserialize(data);
 preorder(root, 0);
 return 0;
}

运行结果为:

8#3#1#6#10#15#
[8]
-----[3]
----------[1]
----------[6]
-----[10]
----------[15]