How to sort array in c++

Welcome dear programmers! We are about to discuss the sorting of an array in ascending as well as descending order. Sorting of data basically means arranging or organizing the data in a particular fashion. There are numerous algorithms available but we are using selection sort because its basic, simple and easy. A good understanding of sorting helps us a lot to master concepts of not only arrays but also nested loops. Let's learn sorting.

Algorithm to sort array in c++?

As we already mentioned in the intro, we will use selection sort to sort our array. Let's discuss how it works.

• In selection sort, we logically divide the array into sorted and unsorted portions.
• The sorted portion will have zero elements in the beginning.
• We will find the smallest element in the array and swap it with the first element of the unsorted array.
• After this process, the elements in the sorted array will gradually increase.
• We will repeat this process until we get all the elements from the unsorted to sorted portion.
• At the end of the selection sort, all the elements will be placed in sorted portion and the unsorted portion will be empty.
• If we want to sort the array in descending order, we will find the maximum or largest element in the array instead of the smallest. It's just a small difference.

See the diagram below to understand selection sort in more detail.

How to sort array in ascending order c++?

• Declare an array called "ArrayofInt" to store the data to sort and two int type variables called size and temp. 
• Take input from user in the array using simple for loop.

    int ArrayofInt[100];
    int size;
    int temp;
    //input the unsorted array
    cout << "enter the size of array" << endl;
    cin >> size;
    for (int i = 0; i < size; i++) {
        cout << "Enter at array index " << i << endl;
        cin >> ArrayofInt[i];
    }
    

• Display the unsorted data to the user again using for loop.

    // Printing the unsorted array to user
    cout << "|Unsorted array|" << endl;
    for (int i = 0; i < size; i++) {
        cout << ArrayofInt[i] << " ";
    }
    cout << endl;
  

• Sort the data using the selection sort algorithm.
• avail nested for loop to find the smallest element in the unsorted array.
• Swap the smallest element with the first element of the unsorted array.
• One complete execution of the nested loop with counter "j" finds and swaps the smallest element one time.
• Then the outer loop with counter "i" separates the sorted portion from the unsorted portion of elements in the array.
• After the execution of outer loop "i", all the elements will be in the sorted portion of the array and there will be no element in the unsorted portion.

    //sort array in ascending order using selection sort
    for (int i = 0; i < size - 1; i++) {
        for (int j = i + 1; j < size; j++) {
            if (ArrayofInt[i] > ArrayofInt[j]) {
                //swapping with smallest element of array.
                temp = ArrayofInt[j];
                ArrayofInt[j] = ArrayofInt[i];
                ArrayofInt[i] = temp;
            }
        }
    }

• Now, finally, print the sorted array in ascending order to the user. 

    // printing the sorted array in ascending order.
    cout << "|sorted array|" << endl;
    for (int i = 0; i < size; i++) {
        cout << ArrayofInt[i] << " ";
    }

That's how we sort an array in ascending order using selection sort the algorithm in c++. 

Also read: Important conceptual questions about variables.

Also read: Concepts of conditional statements in c++.

C++ program to sort an array in ascending order?

The complete code of the array sorting program is given below.

#include<iostream>
using namespace std;
int main() {
    int ArrayofInt[100];
    int size;
    int temp;
    //input the unsorted array
    cout << "enter the size of array" << endl;
    cin >> size;
    for (int i = 0; i < size; i++) {
        cout << "Enter at array index " << i << endl;
        cin >> ArrayofInt[i];
    }
    // Printing the unsorted array to user
    cout << "|Unsorted array|" << endl;
    for (int i = 0; i < size; i++) {
        cout << ArrayofInt[i] << " ";
    }
    cout << endl;
    //sort array in ascending order using selection sort
    for (int i = 0; i < size - 1; i++) {
        for (int j = i + 1; j < size; j++) {
            if (ArrayofInt[i] > ArrayofInt[j]) {
                //swapping with smallest element of array.
                temp = ArrayofInt[j];
                ArrayofInt[j] = ArrayofInt[i];
                ArrayofInt[i] = temp;
            }
        }
    }
    // printing the array in ascending order.
    cout << "|sorted array|" << endl;
    for (int i = 0; i < size; i++) {
        cout << ArrayofInt[i] << " ";
    }
    cout << endl;

    return 0;
}

The output of the program:

C++ program to sort an array in descending order?

• Both programs are almost the same. We will use greater than sign this time in the if statement.
• Find the largest element in the array and swap it with the first element of the unsorted array.

The complete code of the array sorting program is given below.

#include<iostream>
using namespace std;
int main() {
    int ArrayofInt[100];
    int size;
    int temp;
    //input the unsorted array
    cout << "enter the size of array" << endl;
    cin >> size;
    for (int i = 0; i < size; i++) {
        cout << "Enter at array index " << i << endl;
        cin >> ArrayofInt[i];
    }
    // Printing the unsorted array to user
    cout << "|Unsorted array|" << endl;
    for (int i = 0; i < size; i++) {
        cout << ArrayofInt[i] << " ";
    }
    cout << endl;
    //sort array in descending order using selection sort
    for (int i = 0; i < size - 1; i++) {
        for (int j = i + 1; j < size; j++) {

                //just write greater than sign instead of less than
            if (ArrayofInt[i] > ArrayofInt[j]) {
                //swapping with largest element of array.
                temp = ArrayofInt[j];
                ArrayofInt[j] = ArrayofInt[i];
                ArrayofInt[i] = temp;
            }
        }
    }
    // printing array in descending order 
    cout << "|sorted in descending order|" << endl;
    for (int i = 0; i < size; i++) {
        cout << ArrayofInt[i] << " ";
    }
    cout << endl;
}

The output of the program:

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I hope you enjoyed sorting arrays in ascending and descending order. We will meet again soon to discuss a new topic related to programming. Thanks for reading and supporting.