UVa 335 - Processing MX Record

Accepted date: 2015-03-08
Ranking (as of 2015-03-08): 34 out of 225
Language: C++

/*
  UVa 335 - Processing MX Records

  To build using Visual Studio 2012:
    cl -EHsc -O2 UVa_335_Processing_MX_Records.cpp
*/

#include <iostream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;

struct MX_record {
  vector<string> pieces_;
  bool operational_;
  int preference_;
  string redirected_name_;
};

void get_pieces(const string& s, vector<string>& pieces)
{
  for (const char *p = s.c_str(), *q = p; *p; ) {
    while (*p && *p != '.')
      p++;
    pieces.push_back(string(q, p - q));
    if (*p)
      q = ++p;
  }
}

bool compare_pieces(const vector<string>& vs, const vector<string>& vt)
{
  int i = vs.size() - 1, j = vt.size() - 1;
  for( ; i >= 0 && j >= 0; i--, j--) {
    if (vs[i] == "*" || vt[j] == "*")
      return true;
    else if (vs[i] != vt[j])
      return false;
  }
  return (i == -1 && j == -1) ? true : false;
}

int main()
{
  string s, line;
  getline(cin, line);
  istringstream iss(line);
  int N;
  iss >> N;
  iss.clear();
  vector<MX_record> MX_records(N);
  for (int i = 0; i < N; i++) {
    MX_records[i].operational_ = true;
    getline(cin, line);
    iss.str(line);
    if (line[0] != ' ') {
      iss >> s;
      get_pieces(s, MX_records[i].pieces_);
    }
    else
      MX_records[i].pieces_ = MX_records[i - 1].pieces_;
    iss >> MX_records[i].preference_ >> MX_records[i].redirected_name_;
    iss.clear();
  }
  while (true) {
    getline(cin, line);
    if (line[0] == 'X')
      break;
    else {
      iss.str(line);
      char c;
      iss >> c >> s;
      iss.clear();
      switch (c) {
      case 'A':
      {
        vector<string> pieces;
        get_pieces(s, pieces);
        int ri = -1;
        for (int i = 0; i < N; i++)
          if (compare_pieces(pieces, MX_records[i].pieces_)) {
            if (MX_records[i].operational_ &&
              (ri == -1 || MX_records[ri].preference_ > MX_records[i].preference_))
              ri = i;
          }
        cout << s << " =>";
        if (ri != -1)
          cout << ' ' << MX_records[ri].redirected_name_;
        cout << endl;
      }
        break;
      case 'U':
        for (int i = 0; i < N; i++)
          if (MX_records[i].redirected_name_ == s)
            MX_records[i].operational_ = true;
        break;
      case 'D':
        for (int i = 0; i < N; i++)
          if (MX_records[i].redirected_name_ == s)
            MX_records[i].operational_ = false;
        break;
      }
    }
  }
  return 0;
}