Sorting

Bubble sort vs Selection sort

Bubble sort and Selection sort both put an array in order, in different ways. Bubble sort: swap neighbors that are out of order. Selection sort: repeatedly pick the smallest remaining value. In the worst case both take O(n²), so the choice comes down to the other differences below.

At a glance

Property	Bubble sort	Selection sort
Technique	Swap neighbors that are out of order	Repeatedly pick the smallest remaining value
Best case time	O(n)	O(n²)
Average case time	O(n²)	O(n²)
Worst case time	O(n²)	O(n²)
Extra space	O(1)	O(1)
Stable (equal values keep their order)	Yes	No
In place (no extra array)	Yes	Yes
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 selection sort when

writing to memory is expensive, since it makes at most n - 1 swaps.

Avoid it when

the data is large, or you hope sorted input will be fast.

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	Selection sort
Mixed	40	29
Already sorted	6	21
Reversed	63	27
Nearly sorted	13	23
Duplicates	47	31

Bubble sort vs Selection sort

At a glance

Choose bubble sort when

Avoid it when

Choose selection sort when

Avoid it when

The same inputs, counted

See them run

More comparisons

Bubble sort vs Selection sort

At a glance

When to choose each

Choose bubble sort when

Avoid it when

Choose selection sort when

Avoid it when

The same inputs, counted

See them run

More comparisons