#include "stdstuff.h"
#include "IntBag.h"

// note that the constructor and size are not mentioned here as their
// implementations are completely specified in the header file

// constructs a bag having "value" copies of "value".
// Quits if value is negative or higher than MAXVALUES.
IntBag::IntBag (int value) {
               
   // first check value
   if (value<0 || value>MAXVALUES) {
      *this = IntBag();
      quit("IntBag::Intbag - value must be between 0 and MAXVALUES.\n");
   }
      
   // value is good, so initialize fields
   count = value;
   for (int i=0; i<count; i++) {
      data[i] = value;
   }
   walkInProgress=false;
}
  

// returns an IntBag with at most two copies of every different element
// of the bag.  If an element occurs once in the bag, it will occur once
// in the result.  If it occurs twice or more in the bag, it will occur
// exactly twice in the result.
IntBag IntBag::maxTwice() const {
       
   int value;
   bool stillWalking;
   
   IntBag result, copy;
   copy = *this; // make a copy of the original bag
   
   // walk through the copy of the bag (we can't walk
   // through the original as we can't change it)
   for (stillWalking=copy.startWalk(value); stillWalking; 
       stillWalking=copy.continueWalk(value)) {
                                              
      // for each element of our copy, if the value is
      // not already in our result, add one copy.
      // If it occurs more than once, add it a second time.
      // Note that the bag will never fill up, as it will
      // have at most the same number of elements as the
      // original.
      if (result.countOccurrences(value)==0) {
         
         // add one copy to result
         result.add(value);
         
         // if there's one occurrence in copy, add it again
         if(copy.countOccurrences(value)>1)
            result.add(value);
         
         // could also add just one copy if it occurs once
         // in copy, and otherwise add two copies 
      }
   }
   // return the result
   return result; 
}
  
// bag is less than other bag if it has fewer elements
bool IntBag::operator<(const IntBag &otherBag) const {
   return count<otherBag.count;
}

// adds a value to the bag.  returns true on success (space available)
// and false on failure (bag full)
bool IntBag::add (int value) {

  if (count == MAXVALUES) return false;

  data[count++] = value;
  walkInProgress = false; // scrub any ongoing walk
  return true;

}


// removes one occurance of the specfied value from the bag.  returns
// true on success (value existed) and false on failure (value did not exist)
bool IntBag::remove (int value) {

  int i;

  for (i = 0; i < count; i++) {
    if (data[i] == value) {
      // we've found the data value.
      // overwrite it with the last data value and adjust the count
      // to reflect the fact that there are now one fewer values in
      // the bag.  note that this works even if the value being removed
      // is the last value in the bag.
      data[i] = data[--count];
      walkInProgress = false; // scrub any ongoing walk
      return true;
    }
  }

  return false;

}


// returns the number of times that the specified value occurs in the bag
int IntBag::countOccurrences (int value) const {

  int i, occurrences = 0;

  for (i = 0; i < count; i++) {
    if (data[i] == value) {
      occurrences++;
    }
  }

  return occurrences;

}


bool IntBag::startWalk (int &value) {

  if (count == 0) return false;

  walkInProgress = true; walkPosition = 0;
  value = data[walkPosition];
  return true;

}


// quits if a walk is not in progress
bool IntBag::continueWalk (int &value) {

  if (!walkInProgress) {
    quit("IntBag::continueWalk invalid call\n");
  }
  if (++walkPosition == count) {
    walkInProgress = false; // we've come to the end of the road
    return false;
  }
  value = data[walkPosition];
  return true;

}


// randomly picks and returns one of the values in the bag.
// quits if the bag is empty.
int IntBag::pickRandom () const {

  int i;

  if (count == 0) {
    quit("IntBag::pickRandom bag is empty\n");
  }

  i = (int) ((rand () / (RAND_MAX + 1.0)) * count);
  return data[i];

}