Bubble sort idea

Compare neighbours, swap, bubble the largest to the end.

Bubble sort logic

Bubble sort sorts an array by comparing adjacent elements and swapping them if they are in the wrong order. This is repeated to the end of the array.

On each pass, the largest element 'bubbles up' to the end of the array. The name comes from this bubbling motion.

One pass

In one pass, you scan the array from start to end and check each adjacent pair. If their order is wrong, swap with arr[j], arr[j+1] = arr[j+1], arr[j].

At the end of a pass, the largest element has reached its final position at the end. The pass is repeated for the remaining elements.

Exercise One pass

Write bubble_one_pass(arr). Compare neighbors, swap if wrong order. Print [1, 2, 3] with print(bubble_one_pass([3, 1, 2])).

Show example solution

def bubble_one_pass(arr):
    # Do one pass
    n = len(arr)
    for j in range(n - 1):
        if arr[j] > arr[j + 1]:
            arr[j], arr[j + 1] = arr[j + 1], arr[j]
    return arr
print(bubble_one_pass([3, 1, 2]))

Test yourself

How does bubble sort work?
- Uses hashing
- Splits the array in half
- Finds the minimum
- Compares neighbors and swaps
Show answer

Compares neighbors and swaps — Bubble sort compares neighbors and swaps.

Swapping

Swap two elements: arr[j], arr[j+1] = arr[j+1], ____

Show answer

Swap two elements: arr[j], arr[j+1] = arr[j+1], arr[j]

Bubble sort idea: match the terms

Bubble sort

Compare neighbors
Pass

Start to end
Swap

Exchange
Largest

Goes to end

Next lesson: One pass

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