Bubble Sort is the most straightforward sorting algorithm that works by repeatedly swapping the adjacent elements if they are in the wrong order. Its worst-case time complexity is high.

How Bubble Sort Works?

begin BubbleSort(list)
  for all elements of list
    if list[j] > list[j+1]
      swap(list[j], list[j+1])
    end if
   end for

 return list

end BubbleSort

I have taken an array of length 5 and in this example, we have to sort this array using bubble sort. We have to use a Nested loop for this: -

Here n=5

The Outer loop runs from 0 to n-5 and the Inner loop runs from 0 to n-i-1

On every run, we have to compare the adjacent element and if the first one is greater then swap them.

Outer loop: i=0

j=0

arr[j] = 5, arr[j+1] = 20

5>20 = false, No Swap

j=1

arr[j] = 20, arr[j+1] = 4

20>4 = true, Swap

j=2

arr[j] = 20, arr[j+1] = 16

20>16 = true, Swap

j=3

arr[j] = 20, arr[j+1] = 2

20>2 = true, Swap

Now, the 1st outer loop end, and 20 is at their correct position

Outer loop: i=1

j=0

arr[j] = 5, arr[j+1] = 4

5>4 = true, Swap

j=1

arr[j] = 5, arr[j+1] = 16

5>16 = false, No Swap

j=2

arr[j] = 16, arr[j+1] = 2

16>2 = true, Swap

Now, the 2nd outer loop end, and 16 20 are at their correct position

Outer loop: i=2

j=0

arr[j] = 4, arr[j+1] = 5

4>5 = false, No Swap

j=1

arr[j] = 5, arr[j+1] = 2

5>2 = true, Swap

Now, the 3rd outer loop end, and 5 16 20 are at their correct position

Outer loop: i=3

j=0

arr[j] = 4, arr[j+1] = 2

4>2 = true, Swap

Now, the 4th outer loop end, and 2 4 5 16 20 are at their correct position and the array is now sorted.

#include<stdio.h>

void swap(int *x, int *y){
  int temp = *x;
  *x = *y;
  *y=temp;
}

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

void main(){
  int arr[] = {5,20,4,16,2};
  int n=5, i, j, temp;
/*
   Bubble Sort
   Here number of elements is 5
*/
    // Outer loop
  for(i=0;i<n-1;i++){
    // Inner loop
    for (j = 0; j < n-i-1; j++){
        /*
        Comparing arr[j+1] with arr[j] (Two adjacent elements)
        And swap them if arr[j] is greater
        */
        if(arr[j+1]<arr[j]){
            // Swap
            swap(&arr[j], &arr[j+1]);
        }
    }
  }
  // Printing the array
  printArray(arr, n);
}