Careercup - Facebook面试题 - 5729456584916992

2014-05-02 00:59

题目链接

原题：

Given a normal binary tree, write a function to serialize the tree into a string representation (returning the string), and also a function to deserialize a serialized string into the original binary tree.

题目：给定一棵二叉树，请设计序列化和反序列化的方法。

解法：我的方法是使用前序遍历来进行序列化，其中大括号"{}"包含了数据序列，用“#”表示空指针。反序列化的思路则相反。

代码：

 // http://www.careercup.com/question?id=5729456584916992
 #include <cstdio>
 #include <string>
 #include <vector>
 using namespace std;

 struct TreeNode {
     int val;
     TreeNode *left;
     TreeNode *right;
     TreeNode(int _val = ): val(_val), left(nullptr), right(nullptr) {};
 };

 class BinaryTreeSerializer {
 public:
     string serialize(TreeNode *root) {
         string res = "{";

         // preorder traversal
         serializeTraversal(root, res);
         res[res.length() - ] = '}';

         return res;
     };

     TreeNode *deserialize(string s) {
         vector<string> data;
         int i, j, len;

         len = (int)s.length();
         i = ;
         while (true) {
             j = i + ;
             while (s[j] != ',' && s[j] != '}') {
                 ++j;
             }
             data.push_back(s.substr(i, j - i));
             i = j + ;
             if (i >= len) {
                 break;
             }
         }

         int iter = ;
         TreeNode *root = nullptr;

         // preorder traversal
         deserializeTraversal(data, root, iter);

         return root;
     };
 private:
     static char ss[];

     void serializeTraversal(TreeNode *root, string &res) {
         if (root == nullptr) {
             res += "#,";
         } else {
             sprintf(ss, "%d", root->val);
             res += string(ss);
             res.push_back(',');
             serializeTraversal(root->left, res);
             serializeTraversal(root->right, res);
         }
     };

     void deserializeTraversal(vector<string> &data, TreeNode *&root, int &iter) {
         ++iter;
         if (data[iter - ] == "#") {
             root = nullptr;
         } else {
             int val;

             sscanf(data[iter - ].c_str(), "%d", &val);
             root = new TreeNode(val);
             deserializeTraversal(data, root->left, iter);
             deserializeTraversal(data, root->right, iter);
         }
     };
 };