C in 100 Seconds: Bubble Sort

Bubble Sort

The simplest sorting algorithm. Compare two adjacent elements — if the left one is bigger, swap them. Do that for every pair, and the largest value bubbles to the end. Repeat until sorted.

How It Works

Two nested loops. The outer loop controls how many passes — each pass pushes one more element into its final position. The inner loop walks through the unsorted portion, comparing neighbors.

The Swap

if (arr[j] > arr[j + 1]) {
  int temp = arr[j];
  arr[j] = arr[j + 1];
  arr[j + 1] = temp;
}

Output

Before: 64 25 12 22 11
After:  11 12 22 25 64

Complexity

O(n squared) — for every element, it potentially compares against every other element. Not efficient for large arrays, but perfectly fine for small ones.

Student code: GitHub