Convert Set to Vector in C++

In C++, std::vectors stores data in the contiguous memory location while std::set stores data in non-contiguous memory location but in some specified order. In this article, we will learn different methods to convert the set to vector in C++.

Using Range Constructor of std::vector

The easiest way to convert the std::set to std::vector is by using the range constructor of std::vector. We just have to pass the iterator to the beginning and end of the std::set container to the ranged constructor of std::vector during its declaration.

Example

C++

// C++ program to Convert Set To Vector using
// range constructor
#include <bits/stdc++.h>
using namespace std;

int main() {
    set<int> s = { 1, 2, 3, 7, 9, 5 };
  
    // Copy all the elements of set into vector
    // constructor range
    vector<int> v(s.begin(), s.end());

    for (int i : v)
        cout << i << " ";
    return 0;
}

Output

1 2 3 5 7 9 

Time Complexity: O(n), where n is the number of elements in set.
Auxiliary Space: O(n)

Using vector::assign() Method

The std::vector::assign() function replaces the current vector elements from the elements of some other valid containers within a specific rang. We can assign the std::set elements to std::vector by passing the iterator to the start and end of the vector to the vector::assign() function.

Example

C++

// C++ program to convert set to vector using
// std::vector::assign()
#include <bits/stdc++.h>
using namespace std;

int main() {
    set<int> s = {1, 2, 3, 7, 9, 5};

    // Create a vector
    vector<int> v;

    // Assigning all elements of set into vector
    // using std::vector::assign() method
    v.assign(s.begin(), s.end());

    for (int i : v)
        cout << i << " ";
    return 0;
}

Output

1 2 3 5 7 9 

Time Complexity: O(n), where n is the number of elements in set.
Auxiliary Space: O(n)

Using std:: copy() Function

The std::copy() inserts elements from a source container into a destination container. The destination container should be large enough to store all elements. Otherwise, we can use std::back_inserter() iterator instead of destination that works is similar to vector::push_back() function.

Example

C++

// C++ program to Convert Set to Vector using
// std::copy() function
#include <bits/stdc++.h>
using namespace std;

int main() {
    set<int> s = { 1, 2, 3, 7, 9, 5 };
  
  	// Create a vector
    vector<int> v;
  
    // Copying all elements to set into vector
    // using std::copy() method
    copy(s.begin(), s.end(), back_inserter(v));

    for (int i : v)
        cout << i << " ";
    return 0;
}

Output

1 2 3 5 7 9 

Time Complexity: O(n), where n is the number of elements in set.
Auxiliary Space: O(n)

Manually Using vector::push_back() Method

We can manually push all the element of set one-by-one into vector using std::push_back() method using a loop. We can use the set::iterators to iterate to access each element of the set or we can use range based for loop.

Example

C++

// C++ program to convert set to vector using
// std::push_back() method
#include <bits/stdc++.h>
using namespace std;

int main() {
    set<int> s = { 1, 2, 3, 7, 9, 5 };
    vector<int> v;

    // Inserting elements into vector using
    // push_back function
    for (auto i: s) 
        v.push_back(i);

    for (int i : v)
        cout << i << " ";
    return 0;
}

Output

1 2 3 5 7 9 

Time Complexity: O(n), where n is the number of elements in set.
Auxiliary Space: O(n)

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