Careercup

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 = 0): 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 = 0;
    while (i < n) {
        if (str[i] == '>') {
            st.pop();
            ++i;
        } else {
            ptr = new TrieNode(str[i]);
            i += 2;
            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 = 0; 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 0;
}