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 = 0): val(_val), left(nullptr), right(nullptr) {};
};

class BinaryTreeSerializer {
public:
    string serialize(TreeNode *root) {
        string res = "{";
        
        // preorder traversal
        serializeTraversal(root, res);
        res[res.length() - 1] = '}';
        
        return res;
    };
    
    TreeNode *deserialize(string s) {
        vector<string> data;
        int i, j, len;
        
        len = (int)s.length();
        i = 1;
        while (true) {
            j = i + 1;
            while (s[j] != ',' && s[j] != '}') {
                ++j;
            }
            data.push_back(s.substr(i, j - i));
            i = j + 1;
            if (i >= len) {
                break;
            }
        }
        
        int iter = 0;
        TreeNode *root = nullptr;
        
        // preorder traversal
        deserializeTraversal(data, root, iter);
        
        return root;
    };
private:
    static char ss[10];
    
    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 - 1] == "#") {
            root = nullptr;
        } else {
            int val;
            
            sscanf(data[iter - 1].c_str(), "%d", &val);
            root = new TreeNode(val);
            deserializeTraversal(data, root->left, iter);
            deserializeTraversal(data, root->right, iter);
        }
    };
};