Insertion and Deletion in STL Set in C++

Insertion

Insertion in STL set can be done by insert() and emplace() operation.

Insert(): Insert() is used to insert elements to the set. Insert operation takes a reference to an object.

List of functions are used:

• st.size() = Returns the size of set. 
• st.insert() = It is used to insert elements to the set.

Example Code

#include <iostream>
#include <set>
#include <string>
#include <cstdlib>
using namespace std;
int main() {
   set<int> st;
   set<int>::iterator it;
   int c, i;
   while (1) {
      cout<<"1.Size of the Set"<<endl;
      cout<<"2.Insert Element into the Set"<<endl;
      cout<<"3.Display the set: "<<endl;
      cout<<"4.Exit"<<endl;
      cout<<"Enter your Choice: ";
      cin>>c;
      switch(c) {
         case 1:
            cout<<"Size of the Set: ";
            cout<<st.size()<<endl;
         break;
         case 2:
            cout<<"Enter value to be inserted: ";
            cin>>i;
            st.insert(i);
         break;
         case 3:
            cout<<"Displaying Set by Iterator: ";
            for (it = st.begin(); it != st.end(); it++) {
               cout << (*it)<<" ";
            }
            cout<<endl;
         break;
         case 4:
            exit(1);
         break;
         default:
            cout<<"Wrong Choice"<<endl;
      }
   }
   return 0;
}

Output

1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit

Enter your Choice: 1
Size of the Set: 0
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit

Enter your Choice: 2
Enter value to be inserted: 4
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit

Enter your Choice: 2
Enter value to be inserted: 6
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit

Enter your Choice: 2
Enter value to be inserted: 8
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit

Enter your Choice: 2
Enter value to be inserted: 10
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit

Enter your Choice: 3
Displaying Set by Iterator: 4 6 8 10
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 4

Exit code: 1

Emplace()

Emplace operation also used to insert elements to the set in-place. It avoids unnecessary copy of object and does the insertion more efficiently than inset operation.

List of functions used:

• st.size() = Returns the size of set. 
• st.emplace() = It is used to insert elements to the set.

Example Code

#include <iostream>
#include <set>
#include <string>
#include <cstdlib>
using namespace std;
int main() {
   set<int> st;
   set<int>::iterator it;
   int c, i;
   while (1) {
      cout<<"1.Size of the Set"<<endl;
      cout<<"2.Insert Element into the Set"<<endl;
      cout<<"3.Display the set: "<<endl;
      cout<<"4.Exit"<<endl;
      cout<<"Enter your Choice: ";
      cin>>c;
      switch(c) {
         case 1:
            cout<<"Size of the Set: ";
            cout<<st.size()<<endl;
         break;
         case 2:
            cout<<"Enter value to be inserted: ";
            cin>>i;
            st.emplace(i);
         break;
         case 3:
            cout<<"Displaying Set by Iterator: ";
            for (it = st.begin(); it != st.end(); it++) {
               cout << (*it)<<" ";
            }
            cout<<endl;
         break;
         case 4:
            exit(1);
         break;
         default:
            cout<<"Wrong Choice"<<endl;
      }
   }
return 0;
}

Output

1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 1
Size of the Set: 0
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 2
Enter value to be inserted: 4
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 6
Wrong Choice
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 2
Enter value to be inserted: 6
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 2
Enter value to be inserted: 7
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 2
Enter value to be inserted: 8
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 3
Displaying Set by Iterator: 4 6 7 8
1.Size of the Set
2.Insert Element into the Set
3.Display the set:
4.Exit
Enter your Choice: 4

Exit code: 1

Deletion

Using erase() function ,we can delete the elements from set by mentioning its argument, either its position, its value or a range of number.

List of functions used here:

• st.size() = Returns the size of set.
• st.insert() = It is used to insert elements to the set.
• st.erase() = To delete the element from the set

Example Code

#include <iostream>
#include <set>
#include <string>
#include <cstdlib>
using namespace std;
int main() {
   set<int> st;
   set<int>::iterator it;
   int c, i;
   while (1) {
      cout<<"1.Size of the Set"<<endl;
      cout<<"2.Insert Element into the Set"<<endl;
      cout<<"3.Delete Element from the Set"<<endl;
      cout<<"4.Display the set: "<<endl;
      cout<<"5.Exit"<<endl;
      cout<<"Enter your Choice: ";
      cin>>c;
      switch(c) {
         case 1:
            cout<<"Size of the Set: ";
            cout<<st.size()<<endl;
         break;
         case 2:
            cout<<"Enter value to be inserted: ";
            cin>>i;
            st.insert(i);
         break;
         case 3:
            cout<<"Enter the element to be deleted: ";
            cin>>i;
            st.erase(i);
         break;
         case 4:
            cout<<"Displaying Set by Iterator: ";
            for (it = st.begin(); it != st.end(); it++) {
               cout << (*it)<<" ";
            }
            cout<<endl;
         break;
         case 5:
            exit(1);
         break;
         default:
            cout<<"Wrong Choice"<<endl;
      }
}
return 0;
}

Output

1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 1
Size of the Set: 0
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 2
Enter value to be inserted: 1
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 2
Enter value to be inserted: 2
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 2
Enter value to be inserted: 3
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 2
Enter value to be inserted: 4
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 4
Displaying Set by Iterator: 1 2 3 4
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 3
Enter the element to be deleted: 2
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit

Enter your Choice: 4
Displaying Set by Iterator: 1 3 4
1.Size of the Set
2.Insert Element into the Set
3.Delete Element from the Set
4.Display the set:
5.Exit
Enter your Choice: 5

Exit code: 1