Sorting a vector in C++
- In C++, you may sort the vector by using the sort() function.
- This is defined in the <algorithm> header file, so you have to include this in your C++ file.
- You may sort the vectors in ascending and descending order
Different ways can be used to sort vectors which are shown in the examples below. For example:
- Lambda expression
- Using sort function
- Writing a custom function
The following examples show using different ways of sorting the vectors in C++ with examples.
A C++ program that uses sort() function for vector sorting in Asc order
In this program, we have created an int type vector with random elements.
Then we sorted the vector in ascending order by using the sort function as follows:
#include <iostream>
#include<vector>
#include <algorithm>
using namespace std;
int main()
{
//Creating a vector
vector <int> vect = { 20, 25, 10, 5, 0 };
// Using for loop to traverse through vector before sorting
cout << "Vector before sorting \n";
for (int x : vect)
cout << x << " ";
//Applying sorting
sort(vect.begin(), vect.end());
// Using for loop to traverse through vector after sorting
cout << "\n\nVector after sorting \n";
for (int x : vect)
cout << x << " ";
return 0;
}
Output:
In the above program:
- A vector is created
- Sort() function is used with two parameters.
- Using two parameters (begin and end) with sort vector in ascending order.
- The vector is displayed before and after sorting.
Sorting vector in descending order program
By using the third parameter in the sort function (greater<int>()), the vector can be sorted in descending order.
Have a look:
#include <iostream>
#include<vector>
#include <algorithm>
using namespace std;
int main()
{
//Creating a vector
vector <int> vect = { 20, 25, 10, 5, 0 };
// Using for loop to traverse through vector before sorting
cout << "Vector before sorting \n";
for (int x : vect)
cout << x << " ";
//Applying sorting in desc order
sort(vect.begin(), vect.end(),greater<int>());
// Display vector elements in desc order
cout << "\n\nVector after sorting \n";
for (int x : vect)
cout << x << " ";
return 0;
}
Output:
The example of char vector sorting in ascending order
Similarly, you may have other types of vectors than int.
In the program below, we are sorting a vector of char type. First in ascending order:
#include <iostream>
#include<vector>
#include <algorithm>
using namespace std;
int main()
{
//Creating a char type vector
vector <char> vect = { 'n','m','a','z','b' };
// Display vector before sorting
cout << "Char Vector before sorting \n";
for (char ch : vect)
cout << ch << " ";
//Applying sorting
sort(vect.begin(), vect.end());
// Display vector elements in Asc order
cout << "\n\nChar Vector after sorting \n";
for (char i : vect)
cout << i << " ";
return 0;
}
Output:
Char vector in Descending order
The program below sorts the char array in desc order by using the third parameter:
#include <iostream>
#include<vector>
#include <algorithm>
using namespace std;
int main()
{
//Creating a char type vector
vector <char> vect = { 'n','m','a','z','b' };
// Display vector before sorting
cout << "Char Vector before sorting \n";
for (char ch : vect)
cout << ch << " ";
//Applying sorting in desc order for char vector
sort(vect.begin(), vect.end(),greater<int>());
// Display vector elements in desc order
cout << "\n\nChar Vector after sorting \n";
for (char i : vect)
cout << i << " ";
return 0;
}
Output:
Using sort() function with lambda to sort a vector
- In this example, we created a character array of five elements.
- Then we used sort() function with lambda as the third parameter to sort vector in descending order:
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main()
{
//Creating a char type vector
vector <char> vect = { 'n','m','a','z','b' };
cout<<"Vector before sorting : ";
for (char i : vect)
{
cout<<" "<<i;
}
//Sorting the vector in desc order by using lambda function
sort(vect.begin(),vect.end(), [](char &a, char &b){ return a>b; });
//Display vector after sorting
cout<<"\n\nVector after sorting : ";
for (char i : vect)
{
cout<<" "<<i;
}
return 0;
}
Output:
You can see, the vector is sorted in descending order.
