How to Sort a Vector in Descending Order Using STL in C++?

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Sorting vector in descending order means arranging the elements in such a way that the first element will be largest, and second element will be second largest and so on.

In C++, the simplest way to sort the vector in descending order is to by using the sort() function with a custom comparator.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v = {6, 8, 2, 9};

    // Sort the vector
    sort(v.begin(), v.end(), greater<>());

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

9 8 6 2 

Explanation: The std::sort() function sorts a vector in ascending order by default. So, greater<>() function object is used to change the sorting order to descending order.

Using sort() with reverse()

If a custom comparator is not available, just use the simple sort() function to sort the vector in ascending order and then reverse the order using reverse() function.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v = {6, 8, 2, 9};

    // Sorting the vector
    sort(v.begin(), v.end());

    // Reversing the vector
    reverse(v.begin(), v.end());

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

9 8 6 2 

Using stable_sort() with Custom Comparator

The stable_sort() function is similar to sort() function, but it preserves the relative order of equal elements.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v = {6, 8, 2, 9};

    // sort the vector
    stable_sort(v.begin(), v.end(), greater<>());

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

9 8 6 2 

Explanation: The stable_sort() function sorts the vector in ascending order. greater<>() is used as comparator to sort the vector in descending order.

Using Multiset

A C++ multiset stores elements in ascending order by default. So, insert all elements from the vector into the multiset, then copy them back to the vector in reverse order.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v = {6, 8, 2, 9};

    // Create multiset from vector
    multiset<int> ms(v.begin(), v.end());
    v.clear();

    // Insert all elements back to vector
  	// in reverse order
    copy(ms.rbegin(), ms.rend(),
         back_inserter(v));

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

9 8 6 2 

Explanation: The multiset rbegin() and rend() return the reverse iterators which are then used by the copy() function to copy all the elements of multiset back to vector in reverse order.