/* Here's the binary search using start and size rather than low and high.  I can't really
   articulate why, but I find this easier to understand than using low and high, especially
   when the search loop ends.  Note how I decrement size by size/2 when I'm discarding the
   first half of the vector.  This is to handle odd and even sizes correctly. */

#include <vector>
#include <algorithm>
#include <iostream>
#include <fstream>
using namespace std;

class Bsearch {
  public:
    void Create(const string &filename);        // Create the vector from the file.
    bool Find(const string &word) const;        // Return whether a word is in the vector.
  protected: 
    vector <string> words;   
};

/* Create() is straightforward -- it reads each words into a vector, and while doing so,
   determines whether the vector is sorted.  If it is not, then it is sorted at the
   end of Create(). */

void Bsearch::Create(const string &filename)
{
  ifstream fin;
  bool sorted;
  string w;

  sorted = true;

  fin.open(filename.c_str());
  if (fin.fail()) throw (string) "Could not open " + filename;
  while (fin >> w) {
    if (words.size() > 0 && w < words[words.size()-1]) sorted = false;
    words.push_back(w);
  }
  if (!sorted) sort(words.begin(), words.end());
}

/* This is the code where I use start and size rather than low and high. */

bool Bsearch::Find(const string &word) const
{
  int start, size, mid;

  start = 0;
  size = words.size();
  if (size == 0) return false;

  while (size > 1) {
    mid = start + size/2;

    /* I guess I like how this code translates logically: */

    if (words[mid] > word) {  /* If word is not in the second half... */
      size /= 2;              /* Discard the second half. */
    } else {
      start += size/2;        /* Otherwise discard the first half. */
      size -= size/2;
    }
  }
  printf("start: %d\n", start);
  return (words[start] == word);
}

/* The main() is straightfoward -- create the dictionary from the file, then find each
   word on standard input. */

int main(int argc, char **argv)
{
  Bsearch b;
  bool verbose, fnd;
  int tfound, total;
  string w;

  try {
    if (argc != 3) throw (string) "usage: a.out dictionary-file verbose(y/n) -- words on stdin.";
    verbose = (argv[2][0] == 'y');

    tfound = 0;
    total = 0;
 
    b.Create(argv[1]);
    while (cin >> w) {
      total++;
      fnd = b.Find(w);
      if (fnd) tfound++;
      if (verbose) printf("%s: %s\n", w.c_str(), (fnd) ? "found" : "not-found");
    }
    printf("Found: %d of %d\n", tfound, total);
  }
 
  catch (const string &s) {
    cerr << s << endl;
    return 1;
  }
}