[LeetCode] Serialize and Deserialize Binary Tree

Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

For example, you may serialize the following tree

    1
   / \
  2   3
     / \
    4   5

as "[1,2,3,null,null,4,5]", just the same as how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

Credits:
Special thanks to @Louis1992 for adding this problem and creating all test cases.

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 /**
  * Definition for a binary tree node.
  * struct TreeNode {
  *     int val;
  *     TreeNode *left;
  *     TreeNode *right;
  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  * };
  */
 class Codec {
 private:
     void _serialize(TreeNode *root, ostringstream &sout) {
         if (root == NULL) {
             sout << "# ";
             return;
         }
         sout << root->val << " ";
         _serialize(root->left, sout);
         _serialize(root->right, sout);
     }
     void _deserialize(TreeNode *&root, istringstream &sin) {
         int val;
         string tmp;
         if (sin >> tmp && tmp != "#") {
             val = stoi(tmp);
         } else {
             return;
         }
         root = new TreeNode(val);
         _deserialize(root->left, sin);
         _deserialize(root->right, sin);
     }
 public:

     // Encodes a tree to a single string.
     string serialize(TreeNode* root) {
         ostringstream sout;
         _serialize(root, sout);
         return sout.str();
     }

     // Decodes your encoded data to tree.
     TreeNode* deserialize(string data) {
         istringstream sin(data);
         TreeNode *root = NULL;
         _deserialize(root, sin);
         return root;
     }
 };

 // Your Codec object will be instantiated and called as such:
 // Codec codec;
 // codec.deserialize(codec.serialize(root));