#include <string>
#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

int main()
{ ifstream fin;
  fin.open("/home/www/dics/web2.txt");
  if (fin.fail())
  { cerr << "could not open dictionmary file\n";
    exit(1); }
  vector <int> positions;
  int pos = 0;
  while (true)
  { string line;
    getline(fin, line);
    if (fin.fail()) break;
    if (line[0] >= 'a' && line[0] <= 'z')
      positions.push_back(pos);
    pos += line.length() + 1; }
  fin.clear();

  cout << "search for: ";
  string wanted;
  cin >> wanted;
  int first = 0, last = positions.size()-1;
  bool found = false;
  while (first <= last)
  { int mid = (first + last)/2;
    fin.seekg(positions[mid]);
    string line;
    getline(fin, line);
    cout << mid << ": " << line << "\n";
    if (wanted == line)
    { cout << "word found at position " << mid << "\n";
      found = true;
      break; }
    if (wanted < line)
      last = mid -1;
    else
      first = mid + 1; }
  if (! found)
    cout << "word not present\n";
  fin.close(); }