Help, I've mixed my week up!

Question

My dog ate my calendar, and now my days are all mixed up. I tried putting it back together, but I keep mixing up the days of the week! I need some help putting my calendar back together, with the days in the correct order.

And since I need my calendar put together as fast as possible, don't waste my time by sending me superfluous bytes. The fewer bytes I have to read, the better!

Input

The days of the week, in any order. Input can be taken as a list of strings, or a space separated string, or any reasonable way of representing 7 strings (one for each day of the week).

The strings themselves are all capitalized, as weekdays should be, so the exact strings are:

Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday

Output

The days of the week, in sorted order (Monday - Sunday, because of course we adhere to ISO 8601). Output can be as a list of strings, or printed with some delimiter.

Disclaimer

Note that this is a kolmogorov-complexity challenge, with the added benefit of being able to use the input to shorten your code. You are not required to use the input if you don't want to. You are also free to use any approach, from a builtin datetime library to hard-coding the output.

Examples

To see example input and output, you can consult this python script.

• lyxal: I hope you've learnt your lesson from this: never leave dogs with calendars.
• Helena: any delimiter allowed?
• maxb: @Helena I'd say any delimiter within reason. I'd prefer space, comma, or newline, but if the language you're using has another default separator, or you'll be able to knock off a few bytes, go for it. Though I will specify that it has to be the same separator between all output words.
• Christian Gibbons: I hope you have learnt your lesson from this: it is a dog-eat-calendar world.
• maxb: @ASCII-only The program should work for any of the \7ドル!\$ different ways to order the days of the week. I used a random shuffle in my example code just to show that the output order is independent of the input order.

Answer 1

Pyth, 7 bytes

o%CN258

Try it online!

Convert each string to a number via treating its ASCII codes as a base 256 number, then take that mod 258, and sort. This gives the mapping

['Monday', 49]
['Tuesday', 75]
['Wednesday', 89]
['Thursday', 99]
['Friday', 103]
['Saturday', 125]
['Sunday', 211]

Same length but less fun is

.P1314S

The 1314th permutation of the sorted input in lexicographic order.

• Adám: How did you find that?
• izzyg: @Adam I just searched the first 1000 moduluses and got very lucky. On average, it should take over 5040 (7!) moduluses to find one that gives a specific ordering, but this one appears quite early.
• user92069: If you ask people "how did you find that", they probably just brute-forced.
• maxb: I wanted to wait a bit before posting my own solution, but you had the exact same idea that I had (and you did it with 7 bytes instead of 8). Good solution!

Answer 2

JavaScript (Node.js), (削除) 37 36 (削除ここまで) 35 bytes

^{This should also work in Chrome and Edge (Chromium)}

Returns a list of strings.

a=>a.sort().sort(_=>-(a=a*595|5)%7)

Try it online!

How?

We first sort the input array in lexicographical order. Whatever the input is, we get:

Friday, Monday, Saturday, Sunday, Thursday, Tuesday, Wednesday

We then invoke sort() a second time with a callback function that, while ignoring its input, generates a sequence of positive and negative values in such a way that the underlying sorting algorithm (insertion sort) is tricked into putting the array in the desired order.

Below is a summary of all steps. Note that because of the bitwise OR, the value stored in \$a\$ is always coerced to a signed 32-bit integer (and so are the 3rd and 4th columns in this table).

 A | B | previous a | -(a*595|5) | mod 7 | new order
-----+-----+-------------+-------------+-------+-----------------------------------
 Fri | Mon | NaN | -5 | -5 | Mon Fri Sat Sun Thu Tue Wed
 Mon | Sat | 5 | -2975 | 0 | unchanged
 Fri | Sat | 2975 | -1770125 | 0 | unchanged
 Fri | Sun | 1770125 | -1053224375 | 0 | unchanged
 Sat | Sun | 1053224375 | 396722091 | 3 | unchanged
 Sat | Thu | -396722091 | -173557135 | -3 | Mon Fri Thu Sat Sun Tue Wed
 Fri | Thu | 173557135 | -187280221 | -2 | Mon Thu Fri Sat Sun Tue Wed
 Mon | Thu | 187280221 | 237418201 | 6 | unchanged
 Fri | Tue | -237418201 | -470091173 | -6 | Mon Thu Tue Fri Sat Sun Wed
 Thu | Tue | 470091173 | -531373695 | -6 | Mon Tue Thu Fri Sat Sun Wed
 Mon | Tue | 531373695 | 1660231379 | 2 | unchanged
 Fri | Wed | -1660231379 | -4807575 | -3 | Mon Tue Thu Wed Fri Sat Sun
 Tue | Wed | 4807575 | 1434460171 | 4 | unchanged
 Thu | Wed | -1434460171 | -1194690159 | -5 | Mon Tue Wed Thu Fri Sat Sun

• Neil: This relies on Node's specific sorting algorithm, so it's not generic ES6.
• Steve Bennett: Wait, you're not using either argument. So whacky.
• Arnauld: @SteveBennett Ah, you're right. I've added a note to clarify.
• Neil: @Arnauld Not sure what you mean by all major JS engines, as I get Wednesday, Monday, Thursday, Tuesday, Friday, Saturday, Sunday in Safari.
• Neil: Yeah, that's much better, thanks.

Answer 3

Pyke, 2 bytes

Pyke has some weird constant built-ins (a link to the Stack Exchange API, the lengths of months as numbers, the names of the days of the week and so on).

~C

Doesn't take input. Try it online!

• maxb: I don't think anyone is going to beat this
• the default.: I won't be surprised if there is some language I forgot about with a 1-byter for this.

Answer 4

JavaScript, 37 characters

e=>[...'1564023'].map(a=>e.sort()[a])

JavaScript, 38 characters

e=>[1,5,6,4,0,2,3].map(a=>e.sort()[a])

Javascript, 39 characters

e=>e.map((a,i)=>e.sort()['1564023'[i]])

Javascript, 45 characters

e=>e.map((a,i)=>e.sort()[[1,5,6,4,0,2,3][i]])

Javascript, 51 characters

e=>(v=e.sort(),v.map((a,i)=>v[[1,5,6,4,0,2,3][i]]))

Javascript, 52 characters

e=>(v=e.sort(),[v[1],v[5],v[6],v[4],v[0],v[2],v[3]])

Javascript, 61 characters

I tried a couple of things, but they were fractionally longer than:

z=>'Monday Tuesday Wednesday Thursday Friday Saturday Sunday'

• Neil: The 54 is 52 because the z= shouldn't have been included in the count.
• Arnauld: I wonder if it would be possible to do e=>e.map((_,n)=>e.sort()[some_magic_with(n)]) instead, but that seems unlikely. ¯\_(ツ)_/¯
• Steve Bennett: Yeah, I pondered something along those lines. There's about 8 characters to play with (assuming the magic is going to contain n and we want 36 characters or fewer total).

Answer 5

APL (Dyalog Unicode) 18.0 beta, 19 bytes

Full program, taking no input.

'Dddd'(1200⌶)⍳7

Returns a list of strings:

┌──────┬───────┬─────────┬────────┬──────┬────────┬──────┐
│Monday│Tuesday│Wednesday│Thursday│Friday│Saturday│Sunday│
└──────┴───────┴─────────┴────────┴──────┴────────┴──────┘

⍳7 Integers 1...7, representing the dates Jan 1–7, 1900

(1200⌶) Format Date-time ("12:00") as follows:

'Dddd' long Day name

• maxb: I get a domain error when trying the code online: line(1,0) : error AC0008: error (DOMAIN ERROR) executing line "'Dddd'(1200⌶)⍳7"
• Adám: @maxb I forgot to remove the TIO link as TIO is on 17.1. Works locally by me. I'll add a link to the docs instead.
• user92069: "The Nineteenth Byte"

Answer 6

Python 3, (削除) 40 (削除ここまで) 38 bytes

-2 bytes thanks to xnor

from calendar import*;print(*day_name)

Try it online!

---

Python 2, (削除) 44 (削除ここまで) 43 bytes

lambda d:sorted(d,key=lambda x:~hash(x)%72)

Try it online!

• xnor: The perfect built-in! I think from calendar import*;print(*day_name) would be allowed.
• xnor: By the way, I've been looking for a solution similar to your sorting one, but with an object method for the key so as to avoid writing a lambda. I had hopes for "...".strip or "...".translate, but it seems none of those can work. Perhaps you have a better idea with this.
• dingledooper: Thanks for the improvement, I clearly missed that! As for my 2nd answer, I will definitely try to shave off bytes if I can. As you said, the lambda takes up quite a few bytes.

Answer 7

Java (JDK), 27 bytes

java.time.DayOfWeek::values

Try it online!

Doing this because the challenge input is very structured, but the output is not structured at all.

No built-ins, 49 bytes

l->l.sort((a,b)->~a[0]*a[4]%-473-~b[0]*b[4]%-473)

Try it online!

Answer 8

APL (Dyalog Unicode), 21 bytes

Anonymous prefix lambda. Port of isaacg's Pyth solution — go upvote that!

{⍵[⍋258|256⊥ ̈⎕UCS ̈⍵]}

Try it online!

{...} "dfn"; argument is ⍵:

⍵[...] reorder the argument into the following order:

⎕UCS ̈⍵ Universal Character Set code points of each string

256⊥ ̈ evaluate each in base-256

258| the division remainder when divided by 258

⍋ grade (permutation that would sort it)

• user92069: You posted 3 different answers for APL...
• Adám: @petStorm Sure, why not? The are completely different in their approaches.

Answer 9

05AB1E, 6 bytes

Port of isaacg's base conversion answer.

Σ1ö29%

Try it online!

Explanation

Σ Filter the input by this function:
 1ö Base-convert it from 256
 1 Constant 256
 Ì Add 2 (= 258)
 % Modulo by this number

05AB1E, 6 bytes

-1 byte thanks to Expired Data

{œŽ5dè

Try it online!

05AB1E, 21 bytes

Σ"TuWeThFrSaSu"2ôåāsÏ

Try it online!

Explanation

Σ Sort by the output of this function.
 "TuWeThFrSaSu"2ô Split every item of that by length of 2.
 å Contains?
 āsÏ Find all truthy indices of that.

• Expired Data: You can get 6 with the other approach too
• Command Master: {œŽ5dè was exactly the same solution I've found o-o
• Grimmy: Using ö instead of β also gives 6 bytes, and doesn't require a footer to pretty-print.
• Kevin Cruijssen: You can remove the footer in that second approach of @ExpiredData by replacing the ' in the input-list with ": try it online. Also, there is an \$n^{th}\$ permutations builtin .I, which is faster than generating all permutations first before indexing: {Ž5d.I (although it's irrelevant for the byte-count).

Answer 10

Wolfram Language (Mathematica), 27 bytes

DayName@{#}&/@198~Range~204

Try it online!

• Adám: I'm confused. Care to explain?
• ZaMoC: @Adám DayName works like this: DayName[date] . So I found another way by using integers. Unfortunately the order didn't work for Friday....
• Adám: How comes the integers are not representing dates in order?
• ZaMoC: I really don't know... range[7] returns {Monday, Tuesday, Wednesday, Thursday, Saturday, Sunday, Monday}. This is not supposed to work with integers. It's an abuse
• Greg Martin: Not really an abuse. The date format that DayName takes can be {year,month,day} (or even have hours/minutes/seconds); or it can be {year,month} in which case the day is assumed to be 1 if needed; or it can even be {year} in which case the month and day are assumed to be 1 if needed. So this code is calculating the day of the week for 1 January 198, 1 January 199, ... through 1 January 204. I believe it's doing so assuming (wrongly) that our current Gregorian calendar extends back indefinitely. ...

Answer 11

APL (Dyalog Unicode), 35 bytes

Anonymous prefix lambda. This one actually sorts its argument and doesn't use any "cheating" built-ins.

{⍵[⍋((∊∘⎕A⊂⊢)'MoTuWeThFrSa')⍳2↑ ̈⍵]}

Try it online!

{...} "dfn"; argument is ⍵:

⍵[...] reorder the argument into the following order:

2↑ ̈ take the first two letters from each input day name

(...)⍳ find the index in the following list (missing items become 1 beyond last index)

(...)'MoTuWeThFrSa' apply the following tacit function to this string:

⊢ the argument

⊂ split on

∊∘⎕A membership of the uppercase Alphabet

⍋ grade (permutation that would sort it)

Answer 12

C (gcc) -m32, 50 bytes

main(i){for(;puts(nl_langinfo(131079+i%7))-i++;);}

Try it online!

Explanation

Simply put, nl_langinfo() is a useful function which returns a particular string given an argument. It just turns out that the argument to pass for obtaining weekday names is 131079 ... 131086. One other thing is that we must add the flag -m32, which is explained nicely in this answer.

• maxb: I was really confused by the -i++ part, does it work because Sunday happens to be 6 letters (and the 7th day of the week)? EDIT: In nl'_langinfo Sunday is the first day of the week, but your i%7 seems to handle that.
• dingledooper: The i variable starts to 1, and is incremented after every iteration. That means we actually start at 131080 instead of 131079. This is on purpose, since as you said, Sunday is the first day of the week when using nl_langinfo. On the last iteration, when i equals 7, the number becomes 131079 because of the modulo, printing Sunday. The reason it terminates after outputting Sunday is because puts returns the length of the string (including newline), so Sunday returns 7. It also happens that i equals 7, so subtracting them exits the loop.

Answer 13

Python 2, (削除) 45 (削除ここまで) 43 bytes

-2 bytes thanks to @xnor!

lambda l:map(sorted(l).pop,[1,4,4,3,0,0,0])

Try it online!

Sort by normal string comparison first, then look up the correct permutation.

---

Python 3, 58 bytes

lambda l:sorted(l,key=lambda s:"TuWeThFrSaSu".find(s[:2]))

Try it online!

Use the first 2 letters of each day to look up the order.

• maxb: Nice that you skip Mo, which results in -1 for Monday.
• xnor: Nice idea with the sorting! Here's a small byte save, though it needs Python 2 since Python 3 produces a map object unless you unpack.
• Surculose Sputum: @xnor Thank you! I was looking at __getitem__, but totally forgot about pop.

Answer 14

Factor, 20 bytes

day-names 1 rotate .

Try it online!

Factor has a built-in sequence for the days of the week, but is starts with Sunday - that's why I need to rotate the items to the right.

Answer 15

T-SQL, 49 bytes

SELECT DATENAME(w,RANK()OVER(ORDER BY d)-1)FROM t

Input is taken as a pre-existing table t with varchar column d, per our IO standards.

My code doesn't actually use the values in the input table in any way, so the input order doesn't matter (nor do the actual strings, they just have to be distinct). Instead, it uses the fact that it has 7 rows, along with the RANK() function, to generate the numbers 1 through 7.

After subtracting 1, these numbers are implicitly cast as dates (0=Mon Jan 1, 0001, 6=Sun Jan 7, 0001), and the DATENAME function returns the corresponding day of the week.

Answer 16

R, 30 bytes

Assuming an English locale

weekdays(as.Date("1/1/1")+0:6)

Try it online!

January 1st of the year 1 is a Monday (according to R).

• JDL: Technically, this only works if your computer is set to a locale such as en_GB where the day names are the same as the question's. I think you are allowed to assume any reasonable locale you like for these sorts of challenges so it's not an invalid answer, but you should perhaps say at the top that you are assuming an English locale.
• Bart-Jan van Rossum: @JDL Thanks, never thought about that

Answer 17

MathGolf, 8 bytes

á{$ûÞ♠$%

Try it online!

Explanation

á{ sort by the output given from a code block
 $ convert to ordinal (base 256)
 ûÞ♠ push "Þ♠"
 $ convert to ordinal (gives 1791)
 % modulo

I had the exact same idea as isaacg's Pyth answer, but in MathGolf I had to use another modulo. I tried every number up to 1000000, and noticed that the ordinal strings for each weekday ended up in the correct order for sorting when taking them modulo 1791.

• Kevin Cruijssen: Tried to find a shorter way to generate 1791, but can't find one unfortunately. I did found an equal-bytes alternative, though: ○しろまる♠~+ (2048+~256).
• maxb: @KevinCruijssen I thought about modifying the input string (e.g. "Monday") or its ordinal, in order to change the 1791 into another nicer number (hopefully a 1-byte builtin), but I didn't investigate further there. Best case scenario is that it saves 2 bytes, which would be tied with 05AB1E.
• Kevin Cruijssen: You mean like removing the first character of the string before the $ or something along those lines?
• maxb: @KevinCruijssen Yes, something along those lines. It could also be squaring the number after the $, or something similar. But there were so many operators to try that I gave up before I started.

Answer 18

Kotlin , 58 bytes

DayOfWeek.values().map{it.name.toLowerCase().capitalize()}

Answer 19

Perl 5, (削除) 33 (削除ここまで) 29 bytes

print+(sort<>)[1,5,6,4,0,2,3]

Try it online! Just another sort/permute answer. Edit: Saved 4 bytes thanks to @Xcali.

• Xcali: Shaved 4 bytes: Try it online!
• Neil: @Xcali Thanks! I don't really know Perl, I was just putting in parentheses until it stopped erroring...
• Xcali: I just found another issue there. Thursday and Friday are reversed in your output.
• Neil: @Xcali Thanks for spotting my typo... (I got the sequence of digits correct in my other answer at least.)

Answer 20

Retina 0.8.2, (削除) 32 (削除ここまで) (削除) 29 (削除ここまで) (削除) 27 (削除ここまで) 26 bytes

Tu
13
T`MWT`E
O`
T`d`MTWuT

Try it online!

Approach: (削除) Replace the first letter of the days with A, B, C, etc. so we can sort them lexicographically. (削除ここまで) Replace the M in Monday with a 0, the T in Tuesday with a 1, the W in Wednesday with a 2, and the T in Thursday with 4. To help golf off a byte, also replace the u in Tuesday with 3

Tu
13
T`MWT`E

Perform the replacements described above (The E inserts even numbers 02468)

O`

Sort lexicographically. At this point, our list of words looks like this:

0onday
13esday
2ednesday
4hursday
Friday
Saturday
Sunday

Notice that Friday, Saturday, and Sunday are already conveniently in alphabetical order.

T`d`MTWuT

Undo the transformations we performed above (The d inserts the range 0-9)

Answer 21

Powershell, 23 bytes

1..6+0|%{[DayOfWeek]$_}

Convert integers to weekday, but bump array by one because .net prefers Sundays.

37 bytes sorting

($args|%{[DayOfWeek]$_}|sort)[1..6+0]

input is string list to args.

• mazzy: 21 bytes

Answer 22

PHP, 39 bytes

for(;$i<7;)echo" ".jddayofweek($i++,1);

Try it online!

Works in Windows but not in TIO, gotta find how to activate the extension.. takes no input.

We could save 4 bytes with an empty delimiter (which is "some delimiter" the question doesn't say a non-empty delimiter) but I'm not that nasty..

EDIT: version that works universally for 1 byte more

PHP, 40 bytes

for(;$i<7;)echo date("l ",1e6+$i++*8e4);

Try it online!

Answer 23

C (gcc) Little Endian Byte Order, ^{(削除) 123 (削除ここまで) \$\cdots\$ (削除) 85 (削除ここまで)} 67 bytes

c(int**a,int**b){a=**a%274%79-**b%274%79;}f(int*s){qsort(s,7,8,c);}

Try it online!

Saved a whopping 18 bytes - and made it shorter than just printing days - thanks to ceilingcat!!!

Function f takes a list of strings as input and sorts it.

How

Reads the first four characters as a 32-bit int, \$i\$, and then calculates \$((i\mod{274})\mod{79})\$:

Monday -> 5
Tuesday -> 7
Wednesday -> 11
Thursday -> 23
Friday -> 47
Saturday -> 59
Sunday -> 61

Then uses qsort to sort the array.

Previous solution

C (gcc), ^{(削除) 72 (削除ここまで)} 70 bytes

Saved 2 bytes thanks to gastropner!!!

f(){puts("Monday Tuesday Wednesday Thursday Friday Saturday Sunday");}

Try it online!

Just prints the days of the week.
(削除) Unfortunately (削除ここまで) Fortunately this (削除) is (削除ここまで) isn't shorter than sorting the input! All thanks to ceilingcat!! :)))

• gastropner: You could save 2 bytes by using puts() instead of printf().
• Noodle9: @gastropner Nice one - thanks! :-)

Answer 24

Bash + Unix utilities, 29 bytes

jot "-wdate +%%A -d7-1-" 7|sh

Try it online!

• maxb: Nice solution, but it isn't ISO 8601 compliant unfortunately. The week should start with Monday for this challenge.
• Mitchell Spector: Fixed. Thanks for pointing it out.

Answer 25

Keg, 15 bytes

"jnsDt[rƳm(7)dQ7⅍

Try it online!

You'd think this was some sort of fancy sorting algorithm, but no. It's simply a compressed string.

• Adám: Meh, I've got 22 in Jelly: "¡²2GỌḌ¹Ẹṙṙ,ßṃþ-wẈÇUx»

Answer 26

Red, 24 bytes

print system/locale/days

Try it online!

Answer 27

J, 10 bytes

1314 A./:~

Try it online!

J Port of isaacg's alternative Pyth solution — please upvote him!

Answer 28

Retina, 40 bytes

^
MTuWThFSaSu
,6L$s`(.+)(?=.*(1円\w+))
2ドル

Try it online! Link shuffles input in header. Explanation:

^
MTuWThFSaSu

Insert unique day name abbreviations.

,6L$s`(.+)(?=.*(1円\w+))
2ドル

Find the first seven duplicate substrings, and output the word containing the duplicate, thus unabbreviating the names.

Answer 29

Charcoal, (削除) 29 (削除ここまで) 25 bytes

≔E7SθW−θυ⊞υ⌊ιE1564023§υIι

Try it online! Link is to verbose version of code. Explanation:

≔E7Sθ

Input the seven days.

W−θυ⊞υ⌊ι

Sort the days lexicographically.

E1564023§υIι

Apply the permutation to the array.

Answer 30

MATL, 4 bytes

23Y2

Built-in ̄\_(ツ)_/ ̄. Takes no input.

Try it online!