C program to sort an array in an ascending order

In C programming, sorting an array in ascending order means arranging elements from smallest to largest value. This is a fundamental operation that can be implemented using various algorithms, with bubble sort being one of the most commonly taught approaches.

Syntax

// Basic bubble sort algorithm
for (i = 0; i < n; i++) {
    for (j = i + 1; j < n; j++) {
        if (arr[i] > arr[j]) {
            // Swap elements
            temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
    }
}

Array Declaration

Before sorting, we need to understand how to declare arrays in C ?

datatype array_name[size];

For example:

int numbers[10];    // Array of 10 integers
float marks[50];    // Array of 50 floating-point numbers

Example: Sorting Array in Ascending Order

The following program demonstrates how to sort an array using the bubble sort algorithm ?

#include <stdio.h>

int main() {
    int num[20];
    int i, j, temp, n;
    
    printf("Enter number of elements in an array: ");
    scanf("%d", &n);
    
    printf("Enter the elements:<br>");
    for (i = 0; i < n; i++) {
        scanf("%d", &num[i]);
    }
    
    // Bubble sort algorithm
    for (i = 0; i < n; i++) {
        for (j = i + 1; j < n; j++) {
            if (num[i] > num[j]) {
                // Swap elements
                temp = num[i];
                num[i] = num[j];
                num[j] = temp;
            }
        }
    }
    
    printf("The numbers in ascending order:<br>");
    for (i = 0; i < n; i++) {
        printf("%d ", num[i]);
    }
    printf("<br>");
    
    return 0;
}

Enter number of elements in an array: 5
Enter the elements:
64
34
25
12
22
The numbers in ascending order:
12 22 25 34 64

How It Works

The bubble sort algorithm works by:

• Nested loops: The outer loop runs for each element, inner loop compares adjacent elements
• Comparison: If num[i] > num[j], elements are swapped
• Swapping: Uses a temporary variable to exchange positions
• Time Complexity: O(n²) for worst case, O(n) for best case

Key Points

• Bubble sort is simple but not efficient for large datasets
• The algorithm makes multiple passes through the array
• After each pass, the largest element "bubbles up" to its correct position
• Space complexity is O(1) as it sorts in-place

Conclusion

Sorting arrays in ascending order using bubble sort is an excellent way to understand basic sorting concepts in C. While not the most efficient algorithm, it provides a clear foundation for learning more advanced sorting techniques like quick sort and merge sort.