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Sorting of Vector of Tuple in C++ (Descending Order)

  • Last Updated : 21 Aug, 2018

What is Vector of Tuple?
A tuple is an object that can hold a number of elements and a vector containing multiple number of such tuple is called a vector of tuple. The elements can be of different data types. The elements of tuples are initialized as arguments in order in which they will be accessed.




// C++ program to demonstrate vector of tuple
#include <bits/stdc++.h>
using namespace std;
int main()
{
    vector<tuple<int, int, int> > v;
    v.push_back(make_tuple(10, 20, 30));
    v.push_back(make_tuple(15, 5, 25));
    v.push_back(make_tuple(3, 2, 1));
  
    // Printing vector tuples
    for (int i = 0; i < v.size(); i++)
        cout << get<0>(v[i]) << " "
             << get<1>(v[i]) << " "
             << get<2>(v[i]) << "\n";
  
    return 0;
}
Output:
10 20 30
15 5 25
3 2 1

 

Different ways to sort vector of tuples

Case 1 : Sorting the vector elements on the basis of first element of tuples in Descending order.
For these instances, we modify the sort() function and we pass a third argument, a call to an user defined explicit function in the sort() function.






// C++ program to demonstrate sorting in
// vector of tuple according to 1st element
// of tuple
#include <bits/stdc++.h>
using namespace std;
// Comparison function to sort the vector elements
// by first element of tuples in descending order
bool sortdesc(const tuple<int, int, int>& a,
              const tuple<int, int, int>& b)
{
    return (get<0>(a) > get<0>(b));
}
int main()
{
    vector<tuple<int, int, int> > v;
    v.push_back(make_tuple(10, 20, 30));
    v.push_back(make_tuple(15, 5, 25));
    v.push_back(make_tuple(3, 2, 1));
  
    // Using sort() function to sort by 1st
    // element of tuple
    sort(v.begin(), v.end(), sortdesc);
    cout << "Sorted Vector of Tuple on basis"
            " of first element of tuple:\n";
    for (int i = 0; i < v.size(); i++)
        cout << get<0>(v[i]) << " "
             << get<1>(v[i]) << " "
             << get<2>(v[i]) << "\n";
  
    return 0;
}
Output:
Sorted Vector of Tuple on basis of first element of tuple:
15 5 25
10 20 30
3 2 1

Case 2 : Sorting the vector elements on the basis of second element of tuples in descending order.
There are instances when we require to sort the elements of the vector on the basis of second elements of tuples. For that, we modify the sort() function and we pass the third argument, a call to a user-defined explicit function in the sort() function.




// C++ program to demonstrate sorting in vector
// of tuple according to 2nd element of tuples
#include <bits/stdc++.h>
using namespace std;
  
// Comparison function to sort the vector elements
// by second element of tuples
bool sortbysec(const tuple<int, int, int>& a,
               const tuple<int, int, int>& b)
{
    return (get<1>(a) > get<1>(b));
}
  
int main()
{
    vector<tuple<int, int, int> > v;
    v.push_back(make_tuple(10, 20, 30));
    v.push_back(make_tuple(15, 5, 25));
    v.push_back(make_tuple(3, 2, 1));
  
    // Using sort() function to sort by 2nd element
    // of tuple
    sort(v.begin(), v.end(), sortbysec);
    cout << "Sorted Vector of Tuple on basis"
            " of Second element of tuple:\n";
  
    for (int i = 0; i < v.size(); i++)
        cout << get<0>(v[i]) << " "
             << get<1>(v[i]) << " "
             << get<2>(v[i]) << "\n";
    return 0;
}
Output:
Sorted Vector of Tuple on basis of Second element of tuple:
10 20 30
15 5 25
3 2 1

Case 3 : Sorting the vector elements on the basis of third element of tuples in descending order.
There are instances when we require to sort the elements of the vector on the basis of third elements of tuples. For that, we modify the sort() function and we pass the third argument, a call to a user-defined explicit function in the sort() function.




// C++ program to demonstrate sorting in vector
// of tuple according to 3rd element of tuple
#include <bits/stdc++.h>
using namespace std;
// Driver function to sort the vector elements
// by third element of tuple
bool sortbyth(const tuple<int, int, int>& a,
              const tuple<int, int, int>& b)
{
    return (get<2>(a) > get<2>(b));
}
  
int main()
{
    vector<tuple<int, int, int> > v;
    v.push_back(make_tuple(10, 20, 30));
    v.push_back(make_tuple(15, 5, 25));
    v.push_back(make_tuple(3, 2, 1));
  
    // Using sort() function to sort by 3rd element
    // of tuple
    sort(v.begin(), v.end(), sortbyth);
    cout << "Sorted Vector of Tuple on basis"
            " of Third element of tuple:\n";
    for (int i = 0; i < v.size(); i++)
        cout << get<0>(v[i]) << " "
             << get<1>(v[i]) << " "
             << get<2>(v[i]) << "\n";
  
    return 0;
}
Output:
Sorted Vector of Tuple on basis of Third element of tuple:
10 20 30
15 5 25
3 2 1
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