Sorting

Bubble sort vs Merge sort

Bubble sort and Merge sort both put an array in order, in different ways. Bubble sort: swap neighbors that are out of order. Merge sort: divide and conquer: split, sort each half, merge. In the worst case merge sort takes O(n log n) while bubble sort takes O(n²), so merge sort scales better on large inputs.

At a glance

Property	Bubble sort	Merge sort
Technique	Swap neighbors that are out of order	Divide and conquer: split, sort each half, merge
Best case time	O(n)	O(n log n)
Average case time	O(n²)	O(n log n)
Worst case time	O(n²)	O(n log n)
Extra space	O(1)	O(n)
Stable (equal values keep their order)	Yes	Yes
In place (no extra array)	Yes	No
Needs sorted input	No	No

Choose bubble sort when

you want the simplest sort to explain, on tiny or almost sorted data.

Avoid it when

the data is large.

Choose merge sort when

you need a guaranteed O(n log n) time or a stable sort.

Avoid it when

memory is tight.

The same inputs, counted

These numbers come from running both real implementations: operations (comparisons plus writes, a swap counting as two writes).

Input	Bubble sort	Merge sort
Mixed	40	34
Already sorted	6	31
Reversed	63	29
Nearly sorted	13	31
Duplicates	47	32

Bubble sort vs Merge sort

At a glance

Choose bubble sort when

Avoid it when

Choose merge sort when

Avoid it when

The same inputs, counted

See them run

More comparisons

Bubble sort vs Merge sort

At a glance

When to choose each

Choose bubble sort when

Avoid it when

Choose merge sort when

Avoid it when

The same inputs, counted

See them run

More comparisons