How to Create a Stack of Set in C++?

In C++ STL, Stacks are a type of container adaptor with LIFO(Last In First Out) type of working, where a new element is added at one end (top) and an element is removed from that end only. Sets are a type of associative container in which each element is unique and in some sorted order. In this article, we will learn how to create a stack of sets in C++.

Example

Input:
mySet1 = {1, 4, 8, 9, 11}
mySet2 = {1, 2, 3, 5, 7}
Output:
myStack: [ {1, 4, 8, 9, 11}
                   {1, 2, 3, 5, 7} ]

Creating a Stack of Sets in C++

To create a std::stack of std::set in C++, we can pass the type of the stack container to be of type std::set as a template parameter while declaration.

Syntax to Declare Stack of Set

stack<set<type>> myStack

C++ Program to Create a Stack of Set

// C++ Program to illustrate how to create a stack of set
#include <iostream>
#include <set>
#include <stack>
using namespace std;

int main()
{
    // Declaring a stack of sets
    stack<set<int> > myStack;

    // Creating some sets
    set<int> set1 = { 1, 2, 3 };
    set<int> set2 = { 4, 5, 6 };
    set<int> set3 = { 7, 8, 9 };

    // Pushing sets into the stack
    myStack.push(set1);
    myStack.push(set2);
    myStack.push(set3);

    // Checking if the stack is empty
    cout << "myStack: " << endl;
    int i = 1;
    while (!myStack.empty()) {
        auto ele = myStack.top();
        cout << "Set" << i++ << ": ";
        for (auto i : ele) {
            cout << i << " ";
        }
        cout << endl;
        myStack.pop();
    }

    return 0;
}

myStack: 
Set1: 7 8 9 
Set2: 4 5 6 
Set3: 1 2 3 

Time complexity: O(N), where N is the number of sets.
Auxiliary Space: O(N)