Careercup - Microsoft面试题 - 5799446021406720

2014-05-12 07:17

题目链接

原题：

Given below is a tree/trie
A
B    c D
e    F
a<b<e<>>c<>d<f<>>>
above string represents the following trie/tree (visualize) and assume that there exisits a serialize method that performs above.
Now, write a deserialize method so that above string to an object model of the following
TreeNode
TreeNode[] children

题目：给定以上的字典树序列化方法，请写出相应的反序列化方法。

解法：观察序列化的字符串，可以发现序列化的规则是“字母<若干个子树>”。用一个栈就可以写出比较简洁的反序列化代码。

代码：

 // http://www.careercup.com/question?id=5799446021406720
 #include <iostream>
 #include <stack>
 #include <string>
 #include <vector>
 using namespace std;

 struct TrieNode {
     char ch;
     vector<TrieNode *> child;
     TrieNode(char _ch = ): ch(_ch), child(vector<TrieNode *>()) {};
 };

 TrieNode *deserializeFromString(const string &str)
 {
     TrieNode *root;
     TrieNode *ptr;
     stack<TrieNode *>  st;

     int i, n;

     root = nullptr;
     n = (int)str.length();
     i = ;
     while (i < n) {
         if (str[i] == '>') {
             st.pop();
             ++i;
         } else {
             ptr = new TrieNode(str[i]);
             i += ;
             if (st.empty()) {
                 root = ptr;
             } else {
                 (st.top()->child).push_back(ptr);
             }
             st.push(ptr);
         }
     }

     return root;
 }

 void preorderTraversal(TrieNode *root)
 {
     if (root == nullptr) {
         return;
     }
     cout << root->ch << ' ';
     for (int i = ; i < (int)root->child.size(); ++i) {
         preorderTraversal(root->child[i]);
     }
 }

 int main()
 {
     TrieNode *root = nullptr;
     string str;

     while (cin >> str) {
         root = deserializeFromString(str);
         preorderTraversal(root);
         cout << endl;
     }

     return ;
 }