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.
/**
* 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 {
public:
vector<string> split(string s) {
vector<string> split_str;
stringstream ss(s);
string tmp;
while (getline(ss, tmp, ',')) {
split_str.push_back(tmp);
}
return split_str;
}
// Encodes a tree to a single string.
vector<string> serialize(TreeNode* root) {
vector<string> serialized;
string ans;
if (root == NULL) {
return serialized;
}
queue<TreeNode *> q;
q.push(root);
while (!q.empty()) {
TreeNode *node = q.front(); q.pop();
if (ans.empty()) {
ans = to_string(node -> val);
} else {
ans += "," + (node != NULL ? to_string(node -> val) : "#");
}
if (node != NULL) {
q.push(node -> left);
q.push(node -> right);
}
}
serialized = split(ans);
int size = serialized.size() - 1;
while (size >= 0) {
if (serialized[size--] != "#") {
break;
}
serialized.erase(serialized.begin() + size + 1);
}
return serialized;
}
// Decodes your encoded data to tree.
TreeNode* deserialize(vector<string> data) {
if (data.empty()) {
return NULL;
}
TreeNode *root = new TreeNode(stoi(data[0]));
int size = data.size(), i = 1;
queue<TreeNode *> q;
q.push(root);
while (i < size && !q.empty()) {
TreeNode *node = q.front(); q.pop();
if (data[i++] != "#") {
node -> left = new TreeNode(stoi(data[i - 1]));
q.push(node -> left);
}
if (data[i++] != "#") {
node -> right = new TreeNode(stoi(data[i - 1]));
q.push(node -> right);
}
}
return root;
}
};
// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.deserialize(codec.serialize(root));
========== Another =========
/**
* 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 {
public:
// Encodes a tree to a single string.
string serialize(TreeNode* root) {
string ans;
if (root == NULL) {
return ans;
}
vector<string> sol;
queue<TreeNode *> q;
q.push(root);
while (!q.empty()) {
TreeNode *node = q.front(); q.pop();
if (node != NULL) {
sol.push_back(to_string(node -> val));
q.push(node -> left);
q.push(node -> right);
} else {
sol.push_back("null");
}
}
formatResponse(ans, sol);
return ans;
}
void formatResponse(string& ans, vector<string>& strList) {
int size = strList.size();
if (size == 0) {
ans = "";
return;
}
for (int i = size - 1; i >= 0; i--) {
if (strList[i] == "null") {
strList.pop_back();
} else {
break;
}
}
for (int i = 0; i < strList.size(); i++) {
if (i == 0) {
ans += strList[i];
} else {
ans += "," + strList[i];
}
}
}
void split(string s, vector<string>& resp, char delim) {
stringstream ss(s);
string str;
while(getline(ss, str, delim)) {
resp.push_back(str);
}
return;
}
void helper(TreeNode *& root, vector<string>& input) {
if (input.size() == 0 || input[0] == "null") {
root = NULL;
return;
}
root = new TreeNode(stoi(input[0]));
queue<TreeNode *> q;
q.push(root);
int size = input.size();
int iter = 1;
while (1) {
if (q.empty() || iter == size) {
break;
}
TreeNode *node = q.front(); q.pop();
if (input[iter] != "null") {
node -> left = new TreeNode(stoi(input[iter]));
q.push(node -> left);
} else {
node -> left = NULL;
}
iter++;
if (iter == size) {
break;
}
if (input[iter] != "null") {
node -> right = new TreeNode(stoi(input[iter]));
q.push(node -> right);
} else {
node -> right = NULL;
}
iter++;
}
}
// Decodes your encoded data to tree.
TreeNode* deserialize(string data) {
TreeNode *root = NULL;
if (data.empty()) {
return root;
}
vector<string> input;
split(data, input, ',');
helper(root, input);
return root;
}
};
// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.deserialize(codec.serialize(root));
* 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 {
public:
vector<string> split(string s) {
vector<string> split_str;
stringstream ss(s);
string tmp;
while (getline(ss, tmp, ',')) {
split_str.push_back(tmp);
}
return split_str;
}
// Encodes a tree to a single string.
vector<string> serialize(TreeNode* root) {
vector<string> serialized;
string ans;
if (root == NULL) {
return serialized;
}
queue<TreeNode *> q;
q.push(root);
while (!q.empty()) {
TreeNode *node = q.front(); q.pop();
if (ans.empty()) {
ans = to_string(node -> val);
} else {
ans += "," + (node != NULL ? to_string(node -> val) : "#");
}
if (node != NULL) {
q.push(node -> left);
q.push(node -> right);
}
}
serialized = split(ans);
int size = serialized.size() - 1;
while (size >= 0) {
if (serialized[size--] != "#") {
break;
}
serialized.erase(serialized.begin() + size + 1);
}
return serialized;
}
// Decodes your encoded data to tree.
TreeNode* deserialize(vector<string> data) {
if (data.empty()) {
return NULL;
}
TreeNode *root = new TreeNode(stoi(data[0]));
int size = data.size(), i = 1;
queue<TreeNode *> q;
q.push(root);
while (i < size && !q.empty()) {
TreeNode *node = q.front(); q.pop();
if (data[i++] != "#") {
node -> left = new TreeNode(stoi(data[i - 1]));
q.push(node -> left);
}
if (data[i++] != "#") {
node -> right = new TreeNode(stoi(data[i - 1]));
q.push(node -> right);
}
}
return root;
}
};
// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.deserialize(codec.serialize(root));
========== Another =========
/**
* 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 {
public:
// Encodes a tree to a single string.
string serialize(TreeNode* root) {
string ans;
if (root == NULL) {
return ans;
}
vector<string> sol;
queue<TreeNode *> q;
q.push(root);
while (!q.empty()) {
TreeNode *node = q.front(); q.pop();
if (node != NULL) {
sol.push_back(to_string(node -> val));
q.push(node -> left);
q.push(node -> right);
} else {
sol.push_back("null");
}
}
formatResponse(ans, sol);
return ans;
}
void formatResponse(string& ans, vector<string>& strList) {
int size = strList.size();
if (size == 0) {
ans = "";
return;
}
for (int i = size - 1; i >= 0; i--) {
if (strList[i] == "null") {
strList.pop_back();
} else {
break;
}
}
for (int i = 0; i < strList.size(); i++) {
if (i == 0) {
ans += strList[i];
} else {
ans += "," + strList[i];
}
}
}
void split(string s, vector<string>& resp, char delim) {
stringstream ss(s);
string str;
while(getline(ss, str, delim)) {
resp.push_back(str);
}
return;
}
void helper(TreeNode *& root, vector<string>& input) {
if (input.size() == 0 || input[0] == "null") {
root = NULL;
return;
}
root = new TreeNode(stoi(input[0]));
queue<TreeNode *> q;
q.push(root);
int size = input.size();
int iter = 1;
while (1) {
if (q.empty() || iter == size) {
break;
}
TreeNode *node = q.front(); q.pop();
if (input[iter] != "null") {
node -> left = new TreeNode(stoi(input[iter]));
q.push(node -> left);
} else {
node -> left = NULL;
}
iter++;
if (iter == size) {
break;
}
if (input[iter] != "null") {
node -> right = new TreeNode(stoi(input[iter]));
q.push(node -> right);
} else {
node -> right = NULL;
}
iter++;
}
}
// Decodes your encoded data to tree.
TreeNode* deserialize(string data) {
TreeNode *root = NULL;
if (data.empty()) {
return root;
}
vector<string> input;
split(data, input, ',');
helper(root, input);
return root;
}
};
// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.deserialize(codec.serialize(root));
========================
/**
* 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 {
public:
vector<string> split(string str) {
stringstream ss(str);
vector<string> ans;
string tmp;
while(getline(ss, tmp, ',')) {
ans.push_back(tmp);
}
return ans;
}
// Encodes a tree to a single string.
string serialize(TreeNode* root) {
queue<TreeNode *> q;
if (root == NULL) {
return "";
}
string ans;
q.push(root);
while (!q.empty()) {
TreeNode *node = q.front(); q.pop();
string code;
if (node != NULL) {
code = to_string(node -> val);
} else {
code = "#";
}
ans += (ans != "" ? "," + code: code);
if (node == NULL) {
continue;
}
q.push(node -> left);
q.push(node -> right);
}
// Check if trimming needed in the last.
return ans;
}
// Decodes your encoded data to tree.
TreeNode* deserialize(string data) {
if (data == "" || data == "#") {
return NULL;
}
vector<string> str_list = split(data);
queue<TreeNode *> q;
TreeNode *root = new TreeNode(stoi(str_list[0]));
q.push(root);
int iter = 1;
while (iter == 0 || !q.empty()) {
TreeNode *node = q.front(); q.pop();
string val = str_list[iter];
if (val != "#") {
node -> left = new TreeNode(stoi(val));
q.push(node -> left);
}
iter++;
if (iter == str_list.size()) {
return root;
}
val = str_list[iter];
if (val != "#") {
node -> right = new TreeNode(stoi(val));
q.push(node -> right);
}
iter++;
if (iter == str_list.size()) {
return root;
}
}
return root;
}
};
// Your Codec object will be instantiated and called as such:
// Codec ser, deser;
// TreeNode* ans = deser.deserialize(ser.serialize(root));
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