Serialize and Deserialize Binary Tree

Desicription

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.

Example:

1
2
3
4
5
6
7
8
9
You may serialize the following tree:

1
/ \
2 3
/ \
4 5

as "[1,2,3,null,null,4,5]"

Clarification: The above format is the same as how LeetCode 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.

Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
/**
* 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& out) {
if(root == nullptr) {
out << "# ";
} else {
out << root->val << " ";
serialize(root->left, out);
serialize(root->right, out);
}
}

TreeNode* deserialize(istringstream& in) {
string val;
in >> val;
if(val == "#") {
return nullptr;
} else {
TreeNode* root = new TreeNode(stoi(val));
root->left = deserialize(in);
root->right = deserialize(in);
return root;
}
}

public:

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

}

// Decodes your encoded data to tree.
TreeNode* deserialize(const string& data) {
istringstream in(data);
return deserialize(in);
}
};
// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.deserialize(codec.serialize(root));