Coding Grandmaster · project 4 of 46 · premium, free for now

Two ways to sort

Write bubble_sort(items) and selection_sort(items). Each returns (sorted_list, swaps) and must not change the list it was given. The program prints both results for the list.

Learn

Sorting puts a list in order. Bubble sort repeatedly swaps neighbours that are the wrong way round. Selection sort finds the smallest remaining item and moves it to the front with a single swap. Both are correct, but they swap a different number of times, and that count is a way to compare them.

Your task

Write bubble_sort(items) and selection_sort(items). Each returns (sorted_list, swaps) and must not change the list it was given. The program prints both results for the list.

Stretch challenge

Which sort does fewer swaps on a reversed list of 10? Why might that matter for a slow disk?

← Halving the search The growth race →

Python

Press Run to see what your program prints.

Keep going in Coding Grandmaster

How fast is it? Counting steps

Write pair_checks(n): two nested loops that count every pair (i, j) with i smaller than j among n items, and return the count. The program prints pair_checks(10).

Start →2

Searching one by one

Write find(items, target) that returns a pair (index, comparisons). If the target is missing, the index is -1 and the comparisons equal the length of the list.

Start →3

Halving the search

Write binary_search(items, target) for a sorted list. Return (index, steps) where steps counts how many middle items you looked at, or (-1, steps) if it is missing.

Start →5

The growth race

For each size in the list print one line like n=10 linear=10 nlogn=33 quadratic=100, where nlogn is int(n * math.log2(n)).

Start →6

Remembering answers

Write fib_naive(n) returning (value, calls) and fib_memo(n, memo) returning the value while counting calls in memo["calls"]. Print the results for 20.

Start →

Practise the idea

📊 Play Sorting Visualizer

Watch bubble, insertion and selection sort organise a row of numbers.

Play now

FAQ

Two ways to sort: common questions

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