I am implementing bag using array in C++. I can not figure out how to let the deleteElement function work. It is suppose to delete given element from the array. I also don't understand why the array is initialized with bool and how the insert function works.
So, I got three questions:\
- How to make the deleteElement function work?
- Why is the array initialized with bool?
- How does the insert function work? It looks like it only adds true value to the array, but when this program prints the array, you will see that the x value is printed out, I can not figure this out.
#include <iostream>
#include <math.h>
#include <algorithm>
using namespace std;
// cin -> add 0 qry 0 del 0 qry 0 quit
// cout -> TF
// add x -> Adds the number x to the bag
// qry x -> Checks if x belongs to the bag then output T, otherwise output F
// del x -> If there is an element x in the bag, remove it, otherwise do nothing.
// quit -> Stops the program
// Exercise: Fun with bags 1 (Here the bag is a set of int values).
/*
Example:
input: add 1 add 2 add 1 del 1 qry 1 qry 2 quit
output: FT
*/
// enumeration type for actions on the bag
enum action {add, qry, del, quit, none};
// translation of strings into actions
action str2action(string s) {
if (s=="add") return add;
if (s=="qry") return qry;
if (s=="del") return del;
if (s=="quit") return quit;
return none;
}
#define BAG_AS_ARRAY_SIZE 10
struct bag {
bool as_array[BAG_AS_ARRAY_SIZE]; // using arrays
};
// Simple function to initialise the bag
void initialise(bag &b){
// Array
for(int i=0; i<BAG_AS_ARRAY_SIZE; i++){
b.as_array[i] = false;
}
}
// function to display the content of the bag
void display_bag(bag b) {
cout << "The bag is : " << endl;
// Array
cout << " - (A) - : " ;
for(int i=0; i<BAG_AS_ARRAY_SIZE; i++){
if(b.as_array[i])
cout << i << " " ;
}
cout << endl;
return;
}
void insert(bag &b,unsigned int x){ //add
// Array
b.as_array[x] = true;
}
void check(bag &b,unsigned int x) //qry
{
bool q = false;
for(int i = 0; i < BAG_AS_ARRAY_SIZE; i++)
{
if(b.as_array[x])
{
q = true;
}
}
if(q == true)
{
cout << "T";
}
if(q == false)
{
cout << "F";
}
cout << endl;
}
void DeleteElement(bag &b, unsigned int x) //del
{
int i;
for (i=0; i<BAG_AS_ARRAY_SIZE; i++)
if (b.as_array[i] == x)
break;
if (i < BAG_AS_ARRAY_SIZE)
{
for (int j=i; j<BAG_AS_ARRAY_SIZE; j++)
b.as_array[j] = b.as_array[j+1];
}
}
// this function deals with actions on a bag
void update(bag &b, action a, unsigned int x){
switch(a){
case add:
insert(b,x);
break;
case qry:
check(b,x);
break;
case del:
DeleteElement(b,x);
break;
case quit:
break;
case none:
break;
default:
break;
}
return;
}
int main()
{
bag my_bag; //We create an array of boolean type.
string my_act_str;
unsigned int x;
initialise(my_bag); //The array is initialised with False, which is 0
bool go_on = true;
while(go_on)
{
display_bag(my_bag);
cout << "What's next? (actions = add x ,qry x ,del x ,quit)" << endl;
cin >> my_act_str;
action act = str2action(my_act_str);
if(act == quit)
{
go_on = false;
}
if(act == add)
{
cin >> x;
update(my_bag,act,x);
}
if(act == qry)
{
cin >> x;
update(my_bag,act,x);
}
if(act == del)
{
cin >> x;
update(my_bag,act,x);
}
}
return 0;
}
Edit: I found out solution for the delete function. It is very easy one:
void delete_element(bag &b, unsigned int x)
{
b.as_array[x] = false;
}
