LeetCode 449. 序列化和反序列化二叉搜索树

思路

BFS,广度优先遍历，通一5位数存储和读取。
由于val是小于等于1e4，五位字符串可以存储。

sprintf(str,”%05d”,num);

将数字通一转化为5位长的字符串。

stoi(data.substr(p,5));

把5位长的字符串转化为数字。
一层一层，从左到右遍历，存储遍历结果，读取构造搜索二叉树也是从左到右即可。

代码

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/**
 * 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:
    void InOrder(string &res,TreeNode* root){
        if(root==nullptr) return;
        queue<TreeNode*> q;
        char data[6];
        q.push(root);
        while(!q.empty()){
            TreeNode* t=q.front();
            q.pop();
            if(t->left!=nullptr) q.push(t->left);
            if(t->right!=nullptr) q.push(t->right);
            sprintf(data,"%05d",t->val);
            res+=data;
        }
    }
    void SetNum(TreeNode* root,int key){
        if(root->val > key){
            if(root->left!=nullptr)
                SetNum(root->left,key);
            else
                root->left=new TreeNode(key);
        } 
        else if(root->val < key){
            if(root->right!=nullptr)
                SetNum(root->right,key);
            else
                root->right=new TreeNode(key);
        }
    }
    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        string res="";
        InOrder(res,root);
        cout<<res<<endl;
        return res;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        TreeNode* res=nullptr;
        TreeNode* temp;
        int p=0;
        while(p+4<data.length()){
            int num=stoi(data.substr(p,5));
            cout<<num<<endl;
            if(res==nullptr){
                res=new TreeNode(num);
            }else{
                SetNum(res,num);
            }
            p+=5;
        }
        return res;
    }
};

// Your Codec object will be instantiated and called as such:
// Codec* ser = new Codec();
// Codec* deser = new Codec();
// string tree = ser->serialize(root);
// TreeNode* ans = deser->deserialize(tree);
// return ans;

参考

  1. https://leetcode.cn/problems/serialize-and-deserialize-bst/ ↩