Mastering Fundamentals: C++ and Data Structures

How to Sort a Vector in C++

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How to Sort a Vector in C++

    Header in C++

    C++ Pointers

    Displaying A to Z characters using a loop: C++ Program

    Working of Jump Statements in C++

    Inline Functions in C++

    Understanding Substr() Function in C++

    Constructor vs Destructor in C++

    Understanding Copy Constructor in C++

    Becoming Friends with Friend Function in C++

    How File Handling Works in C++

    A Detailed Overview of Macros in C++

    List in C++

    A Set Data Structure (STL) In C++

    A Quick Guide to Circular Linked List in C++

    Stack using Linked List in C++

    How to Sort a Vector in C++

    What are Priority Queues in C++?

    Guide To 5 Data Structures In C++

A vector in C++ is similar to dynamic arrays which are capable of resizing itself if required. The C++ stl provides us sort() inbuilt function to sort a vector

Sorting a vector in ascending order

The following syntax sorts a vector in ascending order:

Syntax

sort(vector.begin(), vector.end())

The above syntax sorts a vector in ascending order. Let us consider the following program,

Source Code

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

int main() {
   
    // Create a vector
    vector<int> myVector = {10,30,40,20};
   
    // Push back 90 at the end of the vector
    myVector.push_back(90);
   
    // Push back 80 at the end of the vector
    myVector.push_back(80);
   
    // Sort the vector
    sort(myVector.begin(), myVector.end());
   
    for(auto it = myVector.begin() ; it != myVector.end() ; it++)
    {
        cout << (*it) <<  ' ';
    }
   
    return 0;
}

Output

Output Description

As you can see, the vector has been sorted in ascending order.

Sorting a vector in descending order

The sort() function accepts a third argument that sorts the vector in descending order. Its syntax is given below,

Syntax

sort(myVector.begin(), myVector.end(), greater<int>())

Let us consider the following program:

Source Code

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

int main() {
   
    // Create a vector
    vector<int> myVector = {10,30,40,20};
   
    // Push back 90 at the end of the vector
    myVector.push_back(90);
   
    // Push back 80 at the end of the vector
    myVector.push_back(80);
   
    // Sort the vector
    sort(myVector.begin(), myVector.end(), greater<int>());
   
    cout << "myVector: { ";
    for(auto it = myVector.begin() ; it != myVector.end() ; it++)
    {
        cout << (*it) <<  ' ';
    }
   
    cout << "}";
   
    return 0;
}

Output:

Output Description

As you can see in the output, the vector has been sorted in descending order.

Sorting a vector in a particular order

The sort() function also accepts a compare function using which we can sort a vector in any particular order. Its syntax is given below,
Syntax

sort(myVector.begin(), myVector.end(), compare)

The compare function should have bool return type and has the following structure:

bool compare(argument1, argument2)
{
 if(condition)
 return true/false;
return true/false;

}

Now let us consider the program that sorts a vector of pairs on the basis of first element:

Source Code

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

// Create compare() function
bool compare(pair<int, int> &a, pair<int, int> &b)
{
    // Compare on the basis of first value
    if(a.first < b.first)
        return true;
    return false;
}

int main() {
   
    // Create a vector of pairs
    vector<pair<int,int>> myVector = {{10,20}, {30, 40}, {20,40}, {20,60}};
  
    // Sort the vector
    // on the basis of first value
    sort(myVector.begin(), myVector.end(), compare);
   
    // Print vector elements
    cout << "myVector: { ";
    for(auto it = myVector.begin() ; it != myVector.end() ; it++)
    {
        cout << '{' << it -> first << ',' << it -> second <<  '}' << " ";
    }
   
    cout << "}";
   
    return 0;
}

write your code here: Coding Playground

Output

Output description

As you can see in the output, elements have been sorted on the basis of first element of pairs in the vector

Conclusion

In this article, we discussed how can sort a vector in C++. In the end we also illustrated how we can sort a vector on the basis of a particular condition by passing a compare function to the sort() function. We believe that this article has surely helped you to enhance your knowledge.