Sort the array into descending order.

Learn how to implement Bubble Sort for descending order in C

bubble_sort_descending.c

#include <stdio.h>

int main() {
    int arr[100], n, i, j, temp;

    // Input size of array
    printf("Enter the number of elements: ");
    scanf("%d", &n);

    // Input elements
    printf("Enter %d elements:\n", n);
    for(i = 0; i < n; i++) {
        printf("arr[%d]: ", i);
        scanf("%d", &arr[i]);
    }

    // Sorting using Bubble Sort (Descending Order)
    for(i = 0; i < n - 1; i++) {
        for(j = 0; j < n - i - 1; j++) {
            if(arr[j] < arr[j + 1]) {
                // Swap elements
                temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
    }

    // Display sorted array
    printf("\nArray in descending order:\n");
    for(i = 0; i < n; i++) {
        printf("arr[%d] = %d\n", i, arr[i]);
    }

    return 0;
}

🧾 Step-by-Step Explanation

🔹 Step 1: Include Header File

#include <stdio.h>

This standard library provides essential functions:

• printf() for displaying output
• scanf() for reading user input
• Basic console I/O operations

🔹 Step 2: Declare Variables and Array

int arr[100], n, i, j, temp;

• arr[100]: Array that can hold up to 100 integers
• n: Actual number of elements to be sorted
• i, j: Loop counters for sorting passes
• temp: Temporary variable for element swapping

🔹 Step 3: Input Size and Elements

printf("Enter the number of elements: ");
scanf("%d", &n);

for(i = 0; i < n; i++) {
    scanf("%d", &arr[i]);
}

• First gets the array size (n ≤ 100)
• Then collects each element from user
• Stores elements in sequential array positions
• Displays index with each input prompt

🔹 Step 4: Sort the Array (Bubble Sort - Descending)

for(i = 0; i < n - 1; i++) {
    for(j = 0; j < n - i - 1; j++) {
        if(arr[j] < arr[j + 1]) {
            temp = arr[j];
            arr[j] = arr[j + 1];
            arr[j + 1] = temp;
        }
    }
}

Modified Bubble Sort for descending order:

• Outer loop: Controls number of passes (n-1 passes needed)
• Inner loop: Compares adjacent elements in each pass
• Comparison: Checks if left element is smaller than right
• Swapping: Exchanges elements if in wrong order
• With each pass, smallest unsorted element "bubbles down"

🔹 Step 5: Display Sorted Array

for(i = 0; i < n; i++) {
    printf("arr[%d] = %d\n", i, arr[i]);
}

• Prints all elements in sorted descending order
• Shows both index and value for each element
• Verifies the successful sorting
• Uses newline character for clean output

🧪 Sample Output

Enter the number of elements: 5
Enter 5 elements:
arr[0]: 25
arr[1]: 40
arr[2]: 10
arr[3]: 60
arr[4]: 30

Array in descending order:
arr[0] = 60
arr[1] = 40
arr[2] = 30
arr[3] = 25
arr[4] = 10

📌 Key Concepts Covered

Bubble Sort Algorithm

A simple comparison-based sorting method with O(n²) time complexity, modified for descending order

Descending Order

Arranging elements from largest to smallest value

Array Processing

Storing and manipulating multiple values in a linear data structure

Element Swapping

Using a temporary variable to exchange two array values

Nested Loop Control

Outer loop for passes; inner loop for element comparison and swapping