push_swap

A 42 sorting-algorithm project. Given a stack of integers, output the shortest possible sequence of allowed stack operations that sorts them.

The challenge

You have two stacks, A and B. A starts with the input integers; B starts empty. Sort A in ascending order using only the operations below — and minimize the move count.

Allowed operations

Op	Effect
sa	Swap the top two elements of A
sb	Swap the top two elements of B
ss	sa and sb simultaneously
pa	Push the top of B onto A
pb	Push the top of A onto B
ra	Rotate A upward (top element becomes last)
rb	Rotate B upward
rr	ra and rb simultaneously
rra	Reverse rotate A (last element becomes first)
rrb	Reverse rotate B
rrr	rra and rrb simultaneously

Approach

Stacks are stored as arrays. The strategy depends on input size:

• ≤ 5 elements — brute-force the optimal sequence
• Larger inputs — a chunk-based / quicksort-style strategy: push partitions of A to B, sort there, then merge back

Edge cases handled: empty input, single element, already-sorted input, duplicate-value rejection, and non-integer / overflow input rejection.

Build

make

Run

./push_swap 3 2 5 1 4

Output is the operation sequence:

pb
pb
ra
pa
pa

Pipe into the 42 checker to verify:

./push_swap 3 2 5 1 4 | ./checker 3 2 5 1 4

Or with a variable:

ARG="3 2 5 1 4"; ./push_swap $ARG | ./checker $ARG

Layout

• push_swap.c, push_swap.h — entry point and headers
• parsing/ — argument parsing, validation, error handling
• operations/ — implementations of sa/sb/ra/rb/pa/pb/rra/rrb/...
• sorting/ — small-case brute force + chunk-based sort
• libft/ — utility functions

Resources

• 42 push_swap subject