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：

 1 // http://www.careercup.com/question?id=5729456584916992

 2 #include <cstdio>

 3 #include <string>

 4 #include <vector>

 5 using namespace std;

 6 

 7 struct TreeNode {

 8     int val;

 9     TreeNode *left;

10     TreeNode *right;

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

12 };

13 

14 class BinaryTreeSerializer {

15 public:

16     string serialize(TreeNode *root) {

17         string res = "{";

18         

19         // preorder traversal

20         serializeTraversal(root, res);

21         res[res.length() - 1] = '}';

22         

23         return res;

24     };

25     

26     TreeNode *deserialize(string s) {

27         vector<string> data;

28         int i, j, len;

29         

30         len = (int)s.length();

31         i = 1;

32         while (true) {

33             j = i + 1;

34             while (s[j] != ',' && s[j] != '}') {

35                 ++j;

36             }

37             data.push_back(s.substr(i, j - i));

38             i = j + 1;

39             if (i >= len) {

40                 break;

41             }

42         }

43         

44         int iter = 0;

45         TreeNode *root = nullptr;

46         

47         // preorder traversal

48         deserializeTraversal(data, root, iter);

49         

50         return root;

51     };

52 private:

53     static char ss[10];

54     

55     void serializeTraversal(TreeNode *root, string &res) {

56         if (root == nullptr) {

57             res += "#,";

58         } else {

59             sprintf(ss, "%d", root->val);

60             res += string(ss);

61             res.push_back(',');

62             serializeTraversal(root->left, res);

63             serializeTraversal(root->right, res);

64         }

65     };

66     

67     void deserializeTraversal(vector<string> &data, TreeNode *&root, int &iter) {

68         ++iter;

69         if (data[iter - 1] == "#") {

70             root = nullptr;

71         } else {

72             int val;

73             

74             sscanf(data[iter - 1].c_str(), "%d", &val);

75             root = new TreeNode(val);

76             deserializeTraversal(data, root->left, iter);

77             deserializeTraversal(data, root->right, iter);

78         }

79     };

80 };