Roll for Initiative!

Question

Roll for Initiative!

Introduction

In tabletop games like Dungeons and Dragons, when you begin a battle, all involved parties roll for initiative. In DnD 5e, this is 1d20 + DEX + Other bonuses, where DEX is the bonus given by your Dexterity stat. The characters that roll higher numbers go first. We'll use a similar, deterministic system in this challenge.

The Challenge

Write a program or function that, when given a list of characters, will output a list of characters in order of initiative.

A character is defined as this:

character = {
    name: "name" // a string
    statblock: [SPD, DEX, WHT] // a list of numbers
                               // DEX = dexterity, SPD = speed, WHT = weight
}

The formula for initiative is the following: $$\text{Initiative} = \left\lfloor{ \frac{\text{SPD}^2}{\sqrt{\lvert\text{DEX}\rvert}} }\right\rfloor - \text{WHT}$$

Input

A list of characters, unsorted. This can be a JSON object, a list of lists, a list of dictionaries, a series of strings etc.

It is guaranteed that all names will be unique.

Output

A list of characters, or character names, sorted by initiative order from highest to lowest, based on the above formula.

Rules

IO can be used with any convenient method.
Standard loopholes are forbidden.
This is code-golf, so smallest program wins!

Sample IO

Input --> Output
[[Name, SPD, DEX, WHT], ...]
    --> [[Name, SPD, DEX, WHT], ...] (or [Name, Name, ...])
---------
[[Alice,1,2,3],[Bob,10,5,0],[Charlie,3,2,1]]
    --> [Bob, Charlie, Alice]
// Alice = -3, Bob = 44, Charlie = 5

[[Z,1,1,1],[B,1,1,1],[XY,5,1,1]]
    --> [XY, Z, B]
// Retain the order of characters from the input if they have the same initiative.
// Z = 0, B = 0, XY = 24

[[Neg,-3,-3,-1],[SomeNeg,5,-2,-4],[NoNeg,4,6,8]]
    --> [SomeNeg, Neg, NoNeg]
// Negative values are valid.
// Neg = 6, SomeNeg = 21, NoNeg = -2

[[Flo,1.5,2.5,3.5],[MoreFlo,2,2.5,3.5]]
    --> [[MoreFlo,2,2.5,3.5], [Flo,1.5,2.5,3.5]]
// Floats are also valid.
// Flo = -2.5, MoreFlo = -1.5

[[Lonely,1,2,3]]
    --> [[Lonely,1,2,3]]
// Input with 1 item.

[]
    --> []
// Empty input leads to empty output.

[[Foo,2,1,4], [Baz,5,5,4], [Bar,5,1,4]]
    --> [Bar, Baz, Foo]
// Foo = 0, Bar = 21, Baz = 7

[['Adam', 2, 4, 1], ['Eve', 2, 3, 1]]
--> [Adam, Eve]
// Adam = 2, Eve = 2
// If you do not floor, you'll end up with [Eve, Adam] (Adam = 2, Eve ~= 2.3)

Sandbox link

Something I came up with on the fly while writing this, it's not really based on anything. — bigyihsuan, Dec 8 '19 at 17:12
Can we sort the input in place (i.e whatever is passed into the function will be sorted when the function finishes)? — Noodle9, Dec 8 '19 at 21:54

Community · Accepted Answer · 2020-06-17 09:04:33Z

7

JavaScript (ES7), 73 60 bytes

-13 bytes by just sorting the input without isolating the names, as suggested by @asgallant

Expects a list of [SPD, DEX, WHT, Name].

a=>a.sort((a,b)=>(g=([s,d,w])=>~(s*s/(d*d)**.25)+w)(a)-g(b))

Try it online!

How?

To save a few bytes:

we compute \$-\text{Initiative}-1\$ instead and sort the list the other way around
we compute \$\sqrt{|\text{DEX}|}\$ as \$(\text{DEX}^2)^{\frac{1}{4}}\$

edited Jun 17 '20 at 9:04

Community♦

1

answered Dec 8 '19 at 16:12

Arnauld

147k14 gold badges150 silver badges535 bronze badges

1

\$\begingroup\$ Outputting a list of characters (not just their names) is valid according to the challenge, so you can save a few bytes by dropping the .map call. \$\endgroup\$ – asgallant Dec 9 '19 at 18:20

Add a comment |

Community · Accepted Answer · 2020-06-17 09:04:33Z

05AB1E, 10 8 bytes

Σ`nsÄt÷-

Input in the format and order ["name", WHT, DEX, SPD], and output are the same inner lists sorted from highest to lowest initiative.

-2 bytes thanks to @Grimmy.

Try it online or verify all test cases.

Explanation:

The sort builtin Σ sorts from lowest to highest by default, so I'm using the following modified formula to not only save bytes, but sort from highest to lowest at the same time with this builtin (thanks @Grimmy):
$$Initiative = WHT - \left\lfloor\frac{SPD^2}{\sqrt{\lvert DEX\rvert}}\right\rfloor$$

Σ         # Sort the (implicit) input-list by:
 `        #  Pop and push all values of the inner list separated to the stack
  n       #  Square the SPD at the top of the stack
   s      #  Swap so the DEX is now at the top of the stack
    Ä     #  Take its absolute value
     t    #  Then its square-root
      ÷   #  And integer-divide the squared SPD by this
       -  #  Subtract this from the WHT (to sort in descending instead of ascending order)
          #  (after which the result is output implicitly)

\$\begingroup\$ s-( can be just -. \$\endgroup\$ – Grimmy Dec 9 '19 at 13:10 — Grimmy, Dec 9 '19 at 13:10

Community · Accepted Answer · 2020-06-17 09:04:33Z

3

Japt, 20 18 bytes

ñÈÌ-(Xg1 ²/Xg2a ¬f

Try it

Simply calculates the formula for each character and sorts. Negates the formula to sort in the correct order.

Takes input as a list of lists [Name, SPD, DEX, WHT]. (I could save a byte taking input as [SPD, Name, DEX, WHT] but that feels cheaty.)

edited Jun 17 '20 at 9:04

Community♦

1

answered Dec 8 '19 at 16:39

Quintec

2,8511 gold badge11 silver badges28 bronze badges

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Black Owl Kai · Accepted Answer · 2019-12-13 09:37:36Z

3

Python 3, 63 59 bytes

lambda c:sorted(c,key=lambda x:x[3]-x[1]**2//abs(x[2]**.5))

Try it online!

Pretty straigtforward. Sorts by - initiative to get the right output order.

Python 2, 60 56 bytes

lambda c:sorted(c,key=lambda(a,b,c,d):d-b*b//abs(c)**.5)

Try it online!

thanks to @Chas Brown

edited Dec 13 '19 at 9:37

answered Dec 8 '19 at 17:30

Black Owl Kai

1,0002 silver badges14 bronze badges

1

\$\begingroup\$ In python2, you can shave off 2 bytes via unpacking. (This is one of the few things I don't like in Python 3). \$\endgroup\$ – Chas Brown Dec 8 '19 at 21:40
\$\begingroup\$ I think you are supposed to return a list of just the names,not the entire records. \$\endgroup\$ – Galen Ivanov Dec 9 '19 at 10:14
\$\begingroup\$ @GalenIvanov The Output section of the challenge specifies you can return the whole Character, or the characters name. This answer has chosen the first option. \$\endgroup\$ – Potato44 Dec 9 '19 at 10:41
\$\begingroup\$ @Potato44 Yes, the Sample IO shows different possibilities. \$\endgroup\$ – Galen Ivanov Dec 9 '19 at 11:13
\$\begingroup\$ @ChasBrown Thank you, I tried this because I thought I had seen it somewhere, but it resulted in an error and I didn't think that it could be 2-only. Got it to 60 with b**2 -> b*b. \$\endgroup\$ – Black Owl Kai Dec 9 '19 at 15:02

| Show 1 more comment

scrawl · Accepted Answer · 2020-02-16 20:56:09Z

3

K (oK), 28 bytes

f:{(!x)@>{-z-(x*x)%%y|-y}.'.x}

Try it online!

-10 thanks to ngn :-)

edited Feb 16 '20 at 20:56

answered Dec 8 '19 at 22:40

scrawl

1,1792 silver badges11 bronze badges

\$\begingroup\$ (y;-1*y)0>y -> y|-y, %: -> %, (-z)+ -> -z- \$\endgroup\$ – ngn Feb 16 '20 at 5:34
\$\begingroup\$ @ngn aghhh, the y sign switch was obviously doing too much work in my implementation. your solution seems to obvious in hindsight. i won't forget that! \$\endgroup\$ – scrawl Feb 16 '20 at 20:57

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game0ver · Accepted Answer · 2019-12-09 15:22:17Z

2

Ruby, 44 bytes

->d{d.sort_by{|_,x,y,z|-x*x/y.abs()**1/2+z}}

Try it online!

-3 bytes thanks to @79037662

edited Dec 9 '19 at 15:22

answered Dec 8 '19 at 18:31

game0ver

6312 silver badges14 bronze badges

\$\begingroup\$ You can get rid of the reverse by sorting "backwards": tio.run/##VczNC4IwHMbx@/6K4UnXb@qmRheD6t6l4xix@VIDS/… \$\endgroup\$ – 79037662 Dec 8 '19 at 20:17
\$\begingroup\$ @79037662 thanks! Good point! I also got rid of some extra bytes by replacing indexing with variables! \$\endgroup\$ – game0ver Dec 8 '19 at 20:37
\$\begingroup\$ See the last test case, which fails if you ignore DEX. \$\endgroup\$ – bigyihsuan Dec 9 '19 at 13:59
\$\begingroup\$ No it doesn't, it gives Bar, Baz, Foo which is the test case... \$\endgroup\$ – game0ver Dec 9 '19 at 14:10

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caird coinheringaahing · Accepted Answer · 2019-12-08 16:51:23Z

Add++, 24 bytes

D,g,@#~,p2^$|.5^/i_
L,§g

Try it online!

Inputs and outputs a list of lists representing the characters, in the same order given in the challenge ([Name SPD DEX WHT])

How it works

On the second line, we define an anonymous function that takes in an argument and sorts it on the result of g, defined on the first list.

g starts by reversing its argument and splatting the elements to its stack: #~. It then removes the name and squares the first stat, Speed, (p2^) before square rooting the absolute value of the second stat, Dexterity, ($|.5^). Finally, we integer divide the two (/i) and subtract from Weight (_). This is the opposite to the formula (where Weight is subtracted from the division), as it will cause the sort function in the second line to sort in the order we want. As Add++ uses a stable sort, order is retained if two characters have the same initiative.

Community · Accepted Answer · 2020-06-17 09:04:33Z

1

APL+WIN, 41 bytes

Prompts for a n x 4 matrix where n is the number of rows 1 per character and the columns are Name, SPD, DEX, WHT. The output is a 1 column matrix of character names

m←⎕⋄⊃m[⍒⌊((m[;2]*2)÷(|m[;3])*.5)-m[;4];1]

Try it online!Courtesy of Dyalog Classic

edited Jun 17 '20 at 9:04

Community♦

1

answered Dec 8 '19 at 17:16

Graham

3,9669 silver badges9 bronze badges

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Galen Ivanov · Accepted Answer · 2019-12-09 13:23:06Z

1

Red, 108 107 bytes

-1 byte thanks to raznagul

func[b][extract next sort/skip collect[foreach e
b[keep 0 -(e/2 ** 2 /(e/3 ** 2 ** .25)- e/4)keep e/1]]2 2]

Try it online!

edited Dec 9 '19 at 13:23

answered Dec 9 '19 at 10:04

Galen Ivanov

19.1k3 gold badges19 silver badges56 bronze badges

1

\$\begingroup\$ I don't know red, but shouldn't you be able to replace e/2 * e/2 with e/2 ** 2? \$\endgroup\$ – raznagul Dec 9 '19 at 13:16
\$\begingroup\$ @raznagul Yes,of course. You can see that I did it for e/3 but apparently I forgot to apply it to e/2. Thanks! \$\endgroup\$ – Galen Ivanov Dec 9 '19 at 13:21

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Community · Accepted Answer · 2020-06-17 09:04:33Z

1

Google Sheets, 49 37 bytes

^{^{-12 bytes thanks to Black Owl Kai}}

=Sort(A:A,D:D-B:B^2/Sqrt(Abs(C:C)),1)

Input is in the range A1:D with the four columns being player, speed, dexterity, and weight.

Explanation:
D:D-B:B^2/Sqrt(Abs(C:C)) do the math bit. The values are actually Initiaive * -1 so we can sort them ascending and get the order we want. Otherwise, all the blank rows would be sorted before the player names.
=Sort(A:A,~,1) sorts the player list based on the math bit output.

Test cases:

edited Jun 17 '20 at 9:04

Community♦

1

answered Dec 9 '19 at 16:11

Engineer Toast

6,8681 gold badge19 silver badges43 bronze badges

1

\$\begingroup\$ =Sort(A:A;D:D-B:B^2/Sqrt(Abs(C:C));1) gets rid of the if \$\endgroup\$ – Black Owl Kai Dec 10 '19 at 8:40

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caird coinheringaahing · Accepted Answer · 2019-12-08 17:05:01Z

0

Jelly, 20 bytes

ḊA2¦U*Ø½j.¤UŒH:/€IµÞ

Try it online!

Well, this is horribly hacked together but it works. The Footer in the TIO link simply runs the code over each list then returns just the names. The code itself returns the names and all stats in the same format as the input, namely [Name, SPD, DEX, WHT]

Will post an explanation after any more golfing

answered Dec 8 '19 at 17:05

caird coinheringaahing

31.6k7 gold badges70 silver badges205 bronze badges

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Neil · Accepted Answer · 2019-12-08 18:12:22Z

Charcoal, 36 bytes

ＦＡ⊞υ⟦⁻⌊∕Ｘ⊟ι²₂↔⊟ι⊟ι⊟ι⟧Ｗ⌈υ«≔Φυ¬⁼ικυ⟦⊟ι

Try it online! Takes quadruples in the order name, weight, speed, dexterity. Explanation:

ＦＡ

Loop over the quadruples.

⊞υ⟦⁻⌊∕Ｘ⊟ι²₂↔⊟ι⊟ι⊟ι⟧

Square the dexterity, floor divide by the square rooted absolute speed and subtract the weight, then create a tuple with the result and the name and push that to the predefined list.

Ｗ⌈υ«

While there are still tuples in the list, take the maximum.

≔Φυ¬⁼ικυ

Remove the tuple from the list.

⟦⊟ι

Output the name on its own line.

Nick Kennedy · Accepted Answer · 2019-12-08 20:17:26Z

0

Jelly, 15 14 bytes

ṛ²:A½$}ɗ_@3ƭ/Þ

Try it online!

A monadic link that takes a list of characters as its argument. Each list is structured as [Name, SPD, DEX, WHT]. Returns a list of characters in the desired order.

edited Dec 8 '19 at 20:17

answered Dec 8 '19 at 19:31

Nick Kennedy

12.7k2 gold badges12 silver badges30 bronze badges

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game0ver · Accepted Answer · 2019-12-09 15:22:38Z

0

Python 3.8, 81 bytes

This solution uses the formula as described in the question. As input a dictionary is expected in the following form: {"name":[SPD, DEX, WHT],...}

lambda d:sorted(n:={_:(i:=-a*a/abs(b)**.5+c)for _,(a,b,c)in d.items()},key=n.get)

Try it online!

edited Dec 9 '19 at 15:22

answered Dec 8 '19 at 17:20

game0ver

6312 silver badges14 bronze badges

\$\begingroup\$ See the last test case, which fails if you ignore DEX. \$\endgroup\$ – bigyihsuan Dec 9 '19 at 13:58
\$\begingroup\$ No it doesn't, it gives Bar, Baz, Foo which is the test case... \$\endgroup\$ – game0ver Dec 9 '19 at 14:11

Add a comment |

Community · Accepted Answer · 2020-06-17 09:04:33Z

APL(NARS), chars 40, bytes 80

{⍵≡⍬:⍬⋄↑¨⍵[⍒{(4⊃⍵)-⍨⌊(2*⍨2⊃⍵)÷√∣3⊃⍵}¨⍵]}

test:

  f←{⍵≡⍬:⍬⋄↑¨⍵[⍒{(4⊃⍵)-⍨⌊(2*⍨2⊃⍵)÷√∣3⊃⍵}¨⍵]}
  ⎕fmt ,⊂(('Lonely') 1 2 3)
┌1────────────────┐
│┌4──────────────┐│
││┌6──────┐      ││
│││ Lonely│ 1 2 3││
││└───────┘ ~ ~ ~2│
│└∊──────────────┘3
└∊────────────────┘
  ⎕fmt f,⊂(('Lonely') 1 2 3)
┌1────────┐
│┌6──────┐│
││ Lonely││
│└───────┘2
└∊────────┘
  ⎕fmt (('Alice') 1 2 3)(('Bob') 10 5 0)(('Charlie') 3 2 1)
┌3──────────────────────────────────────────────────┐
│┌4─────────────┐ ┌4────────────┐ ┌4───────────────┐│
││┌5─────┐      │ │┌3───┐       │ │┌7───────┐      ││
│││ Alice│ 1 2 3│ ││ Bob│ 10 5 0│ ││ Charlie│ 3 2 1││
││└──────┘ ~ ~ ~2 │└────┘ ~~ ~ ~2 │└────────┘ ~ ~ ~2│
│└∊─────────────┘ └∊────────────┘ └∊───────────────┘3
└∊──────────────────────────────────────────────────┘
  ⎕fmt f (('Alice') 1 2 3)(('Bob') 10 5 0)(('Charlie') 3 2 1)
┌3─────────────────────────┐
│┌3───┐ ┌7───────┐ ┌5─────┐│
││ Bob│ │ Charlie│ │ Alice││
│└────┘ └────────┘ └──────┘2
└∊─────────────────────────┘
  ⎕fmt f ('Z' 1 1 1)('B' 1 1 1)(('XY') 5 1 1)
┌3────────┐
│┌2──┐    │
││ XY│ Z B│
│└───┘ ¯ ¯2
└∊────────┘
  ⎕fmt f (('Neg') ¯3 ¯3 ¯1)(('SomeNeg') 5 ¯2 ¯4)(('NoNeg') 4 6 8)
┌3─────────────────────────┐
│┌7───────┐ ┌3───┐ ┌5─────┐│
││ SomeNeg│ │ Neg│ │ NoNeg││
│└────────┘ └────┘ └──────┘2
└∊─────────────────────────┘
  ⎕fmt f ⍬
┌0─┐
│ 0│
└~─┘
  ⎕fmt f (('Flo') 1.5 2.5 3.5)(('MoreFlo') 2 2.5 3.5)
┌2────────────────┐
│┌7───────┐ ┌3───┐│
││ MoreFlo│ │ Flo││
│└────────┘ └────┘2
└∊────────────────┘
  ⎕fmt f (('Foo') 2 1 4)(('Baz') 5 5 4)(('Bar') 5 1 4)
┌3───────────────────┐
│┌3───┐ ┌3───┐ ┌3───┐│
││ Bar│ │ Baz│ │ Foo││
│└────┘ └────┘ └────┘2
└∊───────────────────┘
  ⎕fmt f (('Adam') 2 4 1)(('Eve') 2 3 1)
┌2─────────────┐
│┌4────┐ ┌3───┐│
││ Adam│ │ Eve││
│└─────┘ └────┘2
└∊─────────────┘

Xcali · Accepted Answer · 2020-02-17 03:48:35Z

0

Perl 5 `-n`, 72 bytes

sub i{int($_[1]**2/sqrt abs$_[2])-pop}say$$_[0]for sort{i(@$b)-i@$a}eval

Try it online!

answered Feb 17 '20 at 3:48

Xcali

11.4k2 gold badges9 silver badges31 bronze badges

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Community · Accepted Answer · 2020-06-17 09:04:33Z

C++ (clang), ^{324 \$\cdots\$ 232} 204 bytes

Saved 18 46 bytes thanks to cielingcat!!!

#import<regex>
#import<cmath>
#define i(s)int(*s**s/sqrt(abs(s[1])))-s[2]
struct C{std::string n;float s[3];};void f(std::vector<C>&v){std::stable_sort(&v[0],&*end(v),[](C a,C b){return i(a.s)>i(b.s);});}

Try it online!

Ungolfed:

#include <string>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;

struct C {
    string n;
    float s[3];
};
float i(C c) {
    return floor(c.s[0]*c.s[0] / sqrt(abs(c.s[1]))) - c.s[2];
}
void f(vector<C>&v) {
    stable_sort(begin(v), end(v),
        [](C a,C b) {
            return i(a) > i(b);
        });
}

\$\begingroup\$ @ceilingcat Very nice - thanks! :-) \$\endgroup\$ – Noodle9 Feb 27 '20 at 1:13 — Noodle9, Feb 27 '20 at 1:13

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Roll for Initiative!

Roll for Initiative!

Introduction

The Challenge

Input

Output

Rules

Sample IO

17 Answers 17

JavaScript (ES7), 73 60 bytes

How?

05AB1E, 10 8 bytes

Japt, 20 18 bytes

Python 3, 63 59 bytes

Python 2, 60 56 bytes

K (oK), 28 bytes

Ruby, 44 bytes

Add++, 24 bytes

How it works

APL+WIN, 41 bytes

Red, 108 107 bytes

Google Sheets, 49 37 bytes

Jelly, 20 bytes

Charcoal, 36 bytes

Jelly, 15 14 bytes

Python 3.8, 81 bytes

APL(NARS), chars 40, bytes 80

Perl 5 `-n`, 72 bytes

C++ (clang), ^{324 \$\cdots\$ 232} 204 bytes

Ungolfed:

Your Answer

Not the answer you're looking for? Browse other questions tagged code-golf math sorting or ask your own question.

Hot Network Questions

Roll for Initiative!

Roll for Initiative!

Introduction

The Challenge

Input

Output

Rules

Sample IO

17 Answers 17

JavaScript (ES7), 73 60 bytes

How?

05AB1E, 10 8 bytes

Japt, 20 18 bytes

Python 3, 63 59 bytes

Python 2, 60 56 bytes

K (oK), 28 bytes

Ruby, 44 bytes

Add++, 24 bytes

How it works

APL+WIN, 41 bytes

Red, 108 107 bytes

Google Sheets, 49 37 bytes

Jelly, 20 bytes

Charcoal, 36 bytes

Jelly, 15 14 bytes

Python 3.8, 81 bytes

APL(NARS), chars 40, bytes 80

Perl 5 -n, 72 bytes

C++ (clang), 324 \$\cdots\$ 232 204 bytes

Ungolfed:

Your Answer

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Hot Network Questions

Perl 5 `-n`, 72 bytes

C++ (clang), ^{324 \$\cdots\$ 232} 204 bytes