题目描述
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.
Example1:
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.
解题思路
- 序列化与反序列化二叉树
- 注意反序列化二叉树时，需要传一个当前的位置
- 并且需要注意 值为负数的情况，不能用 val = val * 10 + data[index] -‘0’
- 应该用string内置的函数 stoi
- 序列化，防止出现负数
- 第二个传的应该是个引用
/**
* 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) {
if(root == nullptr){
return "";
}
string str;
fun_serialize(root, str);
return str;
}
void fun_serialize(TreeNode* root, string& str){
if(root == nullptr){
str += "#";
return;
}
str += to_string(root -> val);
str += ",";
fun_serialize(root -> left, str);
fun_serialize(root -> right, str);
}
// Decodes your encoded data to tree.
TreeNode* deserialize(string data) {
if(data.size() == 0){
return nullptr;
}
int pos = 0;
return fun_deserialize(data, pos);
}
TreeNode* fun_deserialize(string data, int& pos){
if(data[pos] == '#'){
pos += 1;
return nullptr;
}
int index = pos;
int val = 0;
while(data[index] != ','){
index++;
}
val = stoi(data.substr(pos, index - pos)); // 注意这一点，不应该用 连乘法
TreeNode* root = new TreeNode(val);
pos = index + 1;
root -> left = fun_deserialize(data, pos);
root -> right = fun_deserialize(data, pos);
return root;
}
};
// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.deserialize(codec.serialize(root));
另外一版代码
- 参考花花
- 使用内置的输入输出流进行操作
// Author: Huahua
// Running time: 39 ms
class Codec {
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(string data) {
istringstream in(data);
return deserialize(in);
}
private:
void serialize(TreeNode* root, ostringstream& out) {
if (!root) {
out << "# ";
return;
}
out << root->val << " ";
serialize(root->left, out);
serialize(root->right, out);
}
TreeNode* deserialize(istringstream& in) {
string val;
in >> val;
if (val == "#") return nullptr;
TreeNode* root = new TreeNode(stoi(val));
root->left = deserialize(in);
root->right = deserialize(in);
return root;
}
};
