Sorting an Array (Bubble Sort)

This lesson covers sorting an array in C with bubble sort, a basic operation used constantly in real work. It's for anyone searching "C bubble sort implementation."

Bubble sort is a simple sorting algorithm that repeatedly compares two adjacent values and swaps them if they're out of order. C has no readily-available standard array-sort function, so you'll implement one yourself often.

The example uses a nested for loop, comparing adjacent elements nums[j] and nums[j + 1] in the inner loop, swapping them using a temporary variable, temp, when they're out of order.

A common early mistake is the swap procedure itself. You need to stash a value in a temporary variable first before swapping — forget this, and the original value is lost.

In real projects, there's a faster standard library function, qsort(), but bubble sort is an important algorithm for understanding what's happening under the hood.

📖 Reference code

#include <stdio.h>

int main(void) {
    int nums[] = {5, 3, 8, 1, 9};
    int n = 5;
    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (nums[j] > nums[j + 1]) {
                int temp = nums[j];
                nums[j] = nums[j + 1];
                nums[j + 1] = temp;
            }
        }
    }
    for (int i = 0; i < n; i++) {
        printf("%d ", nums[i]);
    }
    printf("\n");
    return 0;
}

✍️ Your code

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🧪 This site can't compile or run C directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).