序列化和反序列化二叉搜索树
设计一个算法来序列化和反序列化二叉搜索树
对序列化/反序列化算法的工作方式没有限制
您只需确保二叉搜索树可以序列化为字符串,并且可以将该字符串反序列化为最初的二叉搜索树。
1. 非递归先序遍历 + 编码
class Codec {
public:
// Encodes a tree to a single string.
string serialize(TreeNode* root) {
string code = "";
stack<TreeNode*> s;
while(root||!s.empty()){
if(root){
code+=to_string(root->val);
code.push_back('.');//用于分割所有权值
s.push(root);
root = root->left;
}
else{
code.push_back('#');
code.push_back('.');
root = s.top(); s.pop();//回到上一层
root = root->right;//往右走
}
}
return code;
}
// Decodes your encoded data to tree.
TreeNode* deserialize(string data) {
TreeNode* root = new TreeNode(-1);
TreeNode* cur = root;
stack<TreeNode*> s;
istringstream iss(data);
string c;
while (getline(iss, c, '.')){
if(c.size()==0) continue;//跳过空字符串
if(c=="#"){
cur->val = -1;//后面再删除
if(!s.empty()){
cur = s.top(); s.pop();
cur->right = new TreeNode(-1);
cur = cur->right;//移动到右边
}
}
else{
s.push(cur);//储存,还要处理右指针
cur->val = stoi(c);
cur->left = new TreeNode(-1);
cur = cur->left;
}
}
return f(root);
}
TreeNode* f(TreeNode* root){ //剔除空节点
if(!root||root->val==-1) return nullptr;
root->left = f(root->left);
root->right = f(root->right);
return root;
}
};