Push_swap
Because Swap_push isn’t as natural
Summary:
This project will make you sort data on a stack, with a limited set of instructions, using
the lowest possible number of actions. To succeed you’ll have to manipulate various
types of algorithms and choose the most appropriate solution (out of many) for an
optimized data sorting.
Version: 8.1
Contents
I Foreword 2
II Introduction 4
III Objectives 5
IV Common Instructions 6
V Mandatory part 8
V.1 The rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
V.2 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
V.3 The "push_swap" program . . . . . . . . . . . . . . . . . . . . . . . . 10
V.4 Benchmark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
VI Bonus part 13
VI.1 The "checker" program . . . . . . . . . . . . . . . . . . . . . . . . . . 14
VII Submission and peer-evaluation 16
1
Chapter I
Foreword
• C
#include <stdio.h>
int main(void)
{
printf("hello, world\n");
return 0;
}
• ASM
cseg segment
assume cs:cseg, ds:cseg
org 100h
main proc
jmp debut
mess db 'Hello world!$'
debut:
mov dx, offset mess
mov ah, 9
int 21h
ret
main endp
cseg ends
end main
• LOLCODE
HAI
CAN HAS STDIO?
VISIBLE "HELLO WORLD!"
KTHXBYE
• PHP
<?php
echo "Hello world!";
?>
• BrainFuck
++++++++++[>+++++++>++++++++++>+++>+<<<<-]
>++.>+.+++++++..+++.>++.
<<+++++++++++++++.>.+++.------.--------.>+.>.
2
Push_swap Because Swap_push isn’t as natural
• C#
using System;
public class HelloWorld {
public static void Main () {
Console.WriteLine("Hello world!");
}
}
• HTML5
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Hello world !</title>
</head>
<body>
<p>Hello World !</p>
</body>
</html>
• YASL
"Hello world!"
print
• OCaml
let main () =
print_endline "Hello world !"
let _ = main ()
3
Chapter II
Introduction
The Push swap project is a very simple and a highly straightforward algorithm project:
data must be sorted.
You have at your disposal a set of integer values, 2 stacks, and a set of instructions
to manipulate both stacks.
Your goal? Write a program in C called push_swap which calculates and displays
on the standard output the smallest program, made of Push swap language instructions,
that sorts the integers received as arguments.
Easy?
We’ll see...
4
Chapter III
Objectives
Writing a sorting algorithm is always a very important step in a developer’s journey. It
is often the first encounter with the concept of complexity.
Sorting algorithms and their complexity are part of the classic questions discussed
during job interviews. It’s probably a good time to look at these concepts since you’ll
have to face them at some point.
The learning objectives of this project are rigor, use of C, and use of basic algorithms.
Especially focusing on their complexity.
Sorting values is simple. To sort them the fastest way possible is less simple. Especially
because from one integers configuration to another, the most efficient sorting solution can
differ.
5
Chapter IV
Common Instructions
• Your project must be written in C.
• Your project must be written in accordance with the Norm. If you have bonus
files/functions, they are included in the norm check and you will receive a 0 if there
is a norm error inside.
• Your functions should not quit unexpectedly (segmentation fault, bus error, double
free, etc) apart from undefined behaviors. If this happens, your project will be
considered non functional and will receive a 0 during the evaluation.
• All heap allocated memory space must be properly freed when necessary. No leaks
will be tolerated.
• If the subject requires it, you must submit a Makefile which will compile your
source files to the required output with the flags -Wall, -Wextra and -Werror, use
cc, and your Makefile must not relink.
• Your Makefile must at least contain the rules $(NAME), all, clean, fclean and
re.
• To turn in bonuses to your project, you must include a rule bonus to your Makefile,
which will add all the various headers, librairies or functions that are forbidden on
the main part of the project. Bonuses must be in a different file _bonus.{c/h} if
the subject does not specify anything else. Mandatory and bonus part evaluation
is done separately.
• If your project allows you to use your libft, you must copy its sources and its
associated Makefile in a libft folder with its associated Makefile. Your project’s
Makefile must compile the library by using its Makefile, then compile the project.
• We encourage you to create test programs for your project even though this work
won’t have to be submitted and won’t be graded. It will give you a chance
to easily test your work and your peers’ work. You will find those tests especially
useful during your defence. Indeed, during defence, you are free to use your tests
and/or the tests of the peer you are evaluating.
• Submit your work to your assigned git repository. Only the work in the git reposi-
tory will be graded. If Deepthought is assigned to grade your work, it will be done
6
Push_swap Because Swap_push isn’t as natural
after your peer-evaluations. If an error happens in any section of your work during
Deepthought’s grading, the evaluation will stop.
7
Chapter V
Mandatory part
V.1 The rules
• You have 2 stacks named a and b.
• At the beginning:
◦ The stack a contains a random amount of negative and/or positive numbers
which cannot be duplicated.
◦ The stack b is empty.
• The goal is to sort in ascending order numbers into stack a. To do so you have the
following operations at your disposal:
sa (swap a): Swap the first 2 elements at the top of stack a.
Do nothing if there is only one or no elements.
sb (swap b): Swap the first 2 elements at the top of stack b.
Do nothing if there is only one or no elements.
ss : sa and sb at the same time.
pa (push a): Take the first element at the top of b and put it at the top of a.
Do nothing if b is empty.
pb (push b): Take the first element at the top of a and put it at the top of b.
Do nothing if a is empty.
ra (rotate a): Shift up all elements of stack a by 1.
The first element becomes the last one.
rb (rotate b): Shift up all elements of stack b by 1.
The first element becomes the last one.
rr : ra and rb at the same time.
rra (reverse rotate a): Shift down all elements of stack a by 1.
The last element becomes the first one.
rrb (reverse rotate b): Shift down all elements of stack b by 1.
The last element becomes the first one.
rrr : rra and rrb at the same time.
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Push_swap Because Swap_push isn’t as natural
V.2 Example
To illustrate the effect of some of these instructions, let’s sort a random list of integers.
In this example, we’ll consider that both stacks grow from the right.
----------------------------------------------------------------------------------------------------------
Init a and b:
2
1
3
6
5
8
_ _
a b
----------------------------------------------------------------------------------------------------------
Exec sa:
1
2
3
6
5
8
_ _
a b
----------------------------------------------------------------------------------------------------------
Exec pb pb pb:
6 3
5 2
8 1
_ _
a b
----------------------------------------------------------------------------------------------------------
Exec ra rb (equiv. to rr):
5 2
8 1
6 3
_ _
a b
----------------------------------------------------------------------------------------------------------
Exec rra rrb (equiv. to rrr):
6 3
5 2
8 1
_ _
a b
----------------------------------------------------------------------------------------------------------
Exec sa:
5 3
6 2
8 1
_ _
a b
----------------------------------------------------------------------------------------------------------
Exec pa pa pa:
1
2
3
5
6
8
_ _
a b
----------------------------------------------------------------------------------------------------------
Integers from a get sorted in 12 instructions. Can you do better?
9
Push_swap Because Swap_push isn’t as natural
V.3 The "push_swap" program
Program name push_swap
Turn in files Makefile, *.h, *.c
Makefile NAME, all, clean, fclean, re
Arguments stack a: A list of integers
External functs.
• read, write, malloc, free,
exit
• ft_printf and any equivalent
YOU coded
Libft authorized Yes
Description Sort stacks
Your project must comply with the following rules:
• You have to turn in a Makefile which will compile your source files. It must not
relink.
• Global variables are forbidden.
• You have to write a program named push_swap that takes as an argument the stack
a formatted as a list of integers. The first argument should be at the top of the
stack (be careful about the order).
• The program must display the smallest list of instructions possible to sort the stack
a, the smallest number being at the top.
• Instructions must be separated by a ’\n’ and nothing else.
• The goal is to sort the stack with the lowest possible number of operations. During
the evaluation process, the number of instructions found by your program will be
compared against a limit: the maximum number of operations tolerated. If your
program either displays a longer list or if the numbers aren’t sorted properly, your
grade will be 0.
• If no parameters are specified, the program must not display anything and give the
prompt back.
• In case of error, it must display "Error" followed by a ’\n’ on the standard error.
Errors include for example: some arguments aren’t integers, some arguments are
bigger than an integer and/or there are duplicates.
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Push_swap Because Swap_push isn’t as natural
$>./push_swap 2 1 3 6 5 8
sa
pb
pb
pb
sa
pa
pa
pa
$>./push_swap 0 one 2 3
Error
$>
During the evaluation process, a binary will be provided in order to properly check
your program.
It will work as follows:
$>ARG="4 67 3 87 23"; ./push_swap $ARG | wc -l
6
$>ARG="4 67 3 87 23"; ./push_swap $ARG | ./checker_OS $ARG
OK
$>
If the program checker_OS displays "KO", it means that your push_swap came up
with a list of instructions that doesn’t sort the numbers.
The checker_OS program is available in the resources of the project
in the intranet.
You can find a description of how it works in the Bonus Part of this
document.
11
Push_swap Because Swap_push isn’t as natural
V.4 Benchmark
To validate this project, you must perform certain sorts with a minimal number of oper-
ations:
• For a minimalist validation (that implies a minimal grade of 80)), you must be
able to sort 100 random numbers in fewer than 700 operations.
• For maximal project validation and thus to be able to achieve the bonuses, you
must fulfill the first step above, but also for 500 random numbers, there should
be no more than 5500 operations.
All of this will be verified during your evaluation.
If you wish to complete the bonus part, you must thoroughly validate
the project with each benchmark step achieving the highest possible
score.
12
Chapter VI
Bonus part
This project leaves little room for adding extra features due to its simplicity. However,
how about creating your own checker?
Thanks to the checker program, you will be able to check whether
the list of instructions generated by the push_swap program actually
sorts the stack properly.
The bonus part will only be assessed if the mandatory part is
PERFECT. Perfect means the mandatory part has been integrally
done and works without malfunctioning.In this project, this entails
validating all benchmarks without exception. If you have not passed
ALL the mandatory requirements, your bonus part will not be evaluated
at all.
13
Push_swap Because Swap_push isn’t as natural
VI.1 The "checker" program
Program name checker
Turn in files *.h, *.c
Makefile bonus
Arguments stack a: A list of integers
External functs.
• read, write, malloc, free,
exit
• ft_printf and any equivalent
YOU coded
Libft authorized Yes
Description Execute the sorting instructions
• Write a program named checker that takes as an argument the stack a formatted
as a list of integers. The first argument should be at the top of the stack (be careful
about the order). If no argument is given, it stops and displays nothing.
• It will then wait and read instructions on the standard input, each instruction will
be followed by ’\n’. Once all the instructions have been read, the program has to
execute them on the stack received as an argument.
• If after executing those instructions, the stack a is actually sorted and the stack b
is empty, then the program must display "OK" followed by a ’\n’ on the standard
output.
• In every other case, it must display "KO" followed by a ’\n’ on the standard output.
• In case of error, you must display "Error" followed by a ’\n’ on the standard er-
ror. Errors include for example: some arguments are not integers, some arguments
are bigger than an integer, there are duplicates, an instruction doesn’t exist and/or
is incorrectly formatted.
$>./checker 3 2 1 0
rra
pb
sa
rra
pa
OK
$>./checker 3 2 1 0
sa
rra
pb
KO
$>./checker 3 2 one 0
Error
$>./checker "" 1
Error
$>
14
Push_swap Because Swap_push isn’t as natural
You DO NOT have to reproduce the exact same behavior as the provided
binary. It is mandatory to manage errors but it is up to you to
decide how you want to parse the arguments.
The bonus part will only be assessed if the mandatory part is
PERFECT. Perfect means the mandatory part has been integrally
done and works without malfunctioning.In this project, this entails
validating all benchmarks without exception. If you have not passed
ALL the mandatory requirements, your bonus part will not be evaluated
at all.
15
Chapter VII
Submission and peer-evaluation
Turn in your assignment in your Git repository as usual. Only the work inside your repos-
itory will be evaluated during the defense. Don’t hesitate to double check the names of
your files to ensure they are correct.
As these assignments are not verified by a program, feel free to organize your files as
you wish, as long as you turn in the mandatory files and comply with the requirements.
file.bfe:VABB7yO9xm7xWXROeASsmsgnY0o0sDMJev7zFHhwQS8mvM8V5xQQp
Lc6cDCFXDWTiFzZ2H9skYkiJ/DpQtnM/uZ0
16
