[LeetCode] Serialize and Deserialize N-ary Tree N叉搜索树的

发布时间：2020-12-14 04:14:39 所属栏目：大数据来源：网络整理

导读：? 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 an

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 an N-ary tree. An N-ary tree is a rooted tree in which each node has no more than N children. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that an N-ary 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?3-ary?tree

as?[1 [3[5 6] 2 4]]. You do not necessarily need to follow this format,so please be creative and come up with different approaches yourself.

Note:

N?is in the range of?[1,1000]
Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

这道题让我们对N叉树进行序列化和去序列化，序列化就是将一个数据结构或物体转化为一个位序列，可以存进一个文件或者内存缓冲器中，然后通过网络连接在相同的或者另一个电脑环境中被还原，还原的过程叫做去序列化。现在让我们来序列化和去序列化一个二叉树，并给了我们例子。由于我们有了之前那道Serialize and Deserialize Binary Tree对二叉树的序列化和去序列化的基础，那么这道N叉树的方法也是大同小异了。首先

解法一：

class Codec {
public:

    // Encodes a tree to a single string.
    string serialize(Node* root) {
        string res;
        serializeHelper(root,res);
        return res;
    }
    
    void serializeHelper(Node* node,string& res) {
        if (!node) res += "#";
        else {
            res += to_string(node->val) + " " + to_string(node->children.size()) + " ";
            for (auto child : node->children) {
                serializeHelper(child,res);
            }
        }
    }

    // Decodes your encoded data to tree.
    Node* deserialize(string data) {
        istringstream iss(data);
        return deserializeHelper(iss);
    }
    
    Node* deserializeHelper(istringstream& iss) {
        string val = "",size = "";
        iss >> val;
        if (val == "#") return NULL;
        iss >> size;
        Node *node = new Node(stoi(val),{});
        for (int i = 0; i < stoi(size); ++i) {
            node->children.push_back(deserializeHelper(iss));
        }
        return node;
    }
};

解法二：

class Codec {
public:

    // Encodes a tree to a single string.
    string serialize(Node* root) {
        if (!root) return "#";
        string res;
        queue<Node*> q{{root}};
        while (!q.empty()) {
            Node *t = q.front(); q.pop();
            res += to_string(t->val) + " " + to_string(t->children.size()) + " ";
            for (Node *child : t->children) {
                q.push(child);
            }
        }
        return res;
    }

    // Decodes your encoded data to tree.
    Node* deserialize(string data) {
        istringstream iss(data);
        queue<Node*> qNode;
        queue<int> qSize;
        string val = "",size = "";
        iss >> val;
        if (val == "#") return NULL;
        iss >> size;
        Node *res = new Node(stoi(val),{}),*cur = res;
        qNode.push(cur);
        qSize.push(stoi(size));
        while (!qNode.empty()) {
            Node *t = qNode.front(); qNode.pop();
            int len = qSize.front(); qSize.pop();
            for (int i = 0; i < len; ++i) {
                if (!(iss >> val)) break;
                if (!(iss >> size)) break;
                if (val != "#") {
                    cur = new Node(stoi(val),{});
                    qNode.push(cur);
                    qSize.push(stoi(size));
                    t->children.push_back(cur);
                }
            }
        }
        return res;
    }
};

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