Bag Datastructure

An unordered collection of values that may have duplicates.

A bag has a single query function, numberIn(v), which tells how many copies of an element are in the bag, and two modifier functions, add(v) and remove(v).

numberIn(v) = returns no of element in Bag of type v;
add(v) = add a new element v in the bag;
remove(v) = removes all the element from the Bag of type v;
showBag() = prints all the element of the Bag;

Implementation of Bag in cpp(template).

#include < iostream > 
#include < string.h > 

using namespace std;

template  < class Data > 

class Bag
{
 private:
  struct node
  {
   Data data;
   node *link;
  }*ptr;
 public:
  Bag()
  {
   ptr = NULL;
  }
  
  void add(Data a)
  {
   if(ptr==NULL)
   {
    ptr = new node;
    ptr- > data = a;
    ptr- > link = NULL;
   }
   else
   {
    node *temp;
    temp = new node;
    temp- > data = a;
    temp- > link = ptr;
    ptr = temp;
   }
  }
  
  void remove(Data data){
   int present = 0;
   if(ptr==NULL){
    cout <  < "Error !! Bag is empty" <  < endl;
    return;
   }
   else{
    node *temp;
    node *preTemp;
    temp = ptr;
    while(temp != NULL){
     if(temp- > data == data){
      if(temp == ptr){
       ptr = ptr- > link;
       delete temp;
       temp = ptr;
      }
      else if(temp- > link!=NULL){
       preTemp- > link = temp- > link;
       delete temp;
       temp = preTemp;
      }
      else if(temp- > link==NULL){
       preTemp- > link = NULL;
       delete temp;
      }
     }
     else{
      preTemp = temp;
      temp = temp- > link;
     }
    }
   }
  }
  
  int numberIn(Data data){
   int count = 0;
   if(ptr==NULL)
   {
    return count;
   }
   else
   {
    node *temp;
    temp = ptr;
    while(temp != NULL){
     if(temp- > data == data){
      count++;
     }
     temp = temp- > link;
    }
   }
   return count;
  }
  void showBag(){
   node *temp;
   temp = ptr;
   while(temp!=NULL){
    cout <  < " [" <  < temp- > data <  < "] " <  < endl;
    temp = temp- > link;
   }
  }
};



int main()
{
 int input,remove;
 Bag < int > intBag;
 
 for(int i=0;i < 20;i++)
 {
  cin >  > input;
  intBag.add(input);
 }
 intBag.showBag();
 cin >  > remove;
 cout <  < "NumberIN = " <  < intBag.numberIn(1) <  < endl;
 intBag.remove(remove);
 cout <  < "removed" <  < endl;
 intBag.showBag();
}