Get the best of two Arrays

Question

You will be given two arrays of floating-point numbers. Your task is to pair the corresponding elements of the two arrays, and get the maximum of each pair. However, if the two corresponding elements are equal, you must take their sum instead.

For example, given the lists [1, 3, 3.2, 2.3] and [3, 1, 3.2, 2.6], you must do the following:

• Pair the elements (or zip): [[1, 3], [3, 1], [3.2, 3.2], [2.3, 2.6]].

• Go through each pair and apply the process above: [3, 3, 6.4, 2.6].

---

Specs

• The arrays / lists will always have equal length. They may however be empty.

• The numbers they contain will always fit your language's capabilities, as long as you do not abuse that. They may be positive, zero or negative, you must handle all types.

• If it helps you reduce your byte count, you may also take the length of the lists as input.

Rules

• This is code-golf, so shortest answer in bytes wins.
• Standard input and output rules apply. You may take input (and output) in any reasonable format.
• Default Loopholes are forbidden.

---

Test Cases

Array_1, Array_2 -> Output
[], [] -> []
[1, 2, 3], [1, 3, 2] -> [2, 3, 3]
[1, 3, 3.2, 2.3], [3, 1, 3.2, 2.6] -> [3, 3, 6.4, 2.6]
[1,2,3,4,5,5,7,8,9,10], [10,9,8,7,6,5,4,3,2,1] -> [10, 9, 8, 7, 6, 10, 7, 8, 9, 10]
[-3.2, -3.2, -2.4, 7, -10.1], [100, -3.2, 2.4, -7, -10.1] -> [100, -6.4, 2.4, 7, -20.2]

• Wheat Wizard: You say that the numbers will always fit "within your language's" capabilities". As long as you do not "abuse" that. Would only supporting integers in a language that does not have floats be considered an abuse? The question does say floating point but I don't really see a reason why it has to be floats. The same process can be done on integers. I would like to solve this in Brain-Flak but Brain-flak only supports ints.
• user70974: @WheatWizard I can make an exception for that. Go ahead and post your answer and mention I allowed it to avoid confusion.

Answer 1

Japt, 13 bytes

íV,È\Y Ä *XwY

Try it online! with the -Q flag to format the output array.

• Shaggy: Nicely done. I made 2 attempts at this earlier with both coming out at 17 bytes. I'd forgotten í could take a function as a second argument.

Answer 2

J, 6 bytes

>.*1+=

A direct translation of my APL answer (and thus works the same as my MY and Jelly answers). Any tips are welcome, since I don't really know J.

Try it online!

Comparison with APL

>.*1+=
⌈ ×ばつ1+=

Answer 3

Rust, (削除) 107 (削除ここまで) 97 bytes

|a:V,b:V|a.iter().zip(b).map(|(&x,y)|if x==y{x+y}else{x.max(y)}).collect::<V>();
type V=Vec<f32>;

Try it online!

Saved 8 bytes thanks to @mgc

• mgc: I guess you can save 8 bytes by using type inference on the collected Vec and by using the max method of f32s: |a:Vec<f32>,b:Vec<f32>|a.iter().zip(b).map(|(&x,y)|if x==y{x+y}else{x.max(y)}).collect::<Vec<_>>();
• jferard: @mgc Thanks! Type inference was a good idea, but in this case type alias is even shorter.

Answer 4

Scala, 61 Bytes

x=>y=>x zip y map(v=>if(v._1==v._2)v._1*2 else v._1 max v._2)

The above is a function literal in Scala. Here's an explanation.

x=>y=> // Function literal taking 2 * Vector[Float], x and y.
x zip y // Zip x and y into one list of pairs.
map( // Replace every element in the list via a function.
v=> // Function literal that takes a pair of floats.
if(v._1==v._2) // If the pair are equal.
v._1*2 // Set the element to the first member of the pair multiplied by 2.
else // Otherwise.
v._1 max v._2) // Set it to their max.

Answer 5

Swift 4, 41 bytes

{zip(0,ドル1ドル).map{0ドル==1ドル ?2*0ドル:max(0,ドル1ドル)}}

Test cases:

let f: ([Float], [Float]) -> [Float]
 = {zip(0,ドル1ドル).map{0ドル==1ドル ?2*0ドル:max(0,ドル1ドル)}}
let testcases: [(inputA: [Float], inputB: [Float], expected: [Float])] = [
 (
 inputA: [],
 inputB: [],
 expected: []
 ),
 (
 inputA: [1, 2, 3],
 inputB: [1, 3, 2],
 expected: [2, 3, 3]
 ),
 (
 inputA: [1, 3, 3.2, 2.3],
 inputB: [3, 1, 3.2, 2.6],
 expected: [3, 3, 6.4, 2.6]
 ),
 (
 inputA: [1,2,3,4,5,5,7,8,9,10],
 inputB: [10,9,8,7,6,5,4,3,2,1],
 expected: [10, 9, 8, 7, 6, 10, 7, 8, 9, 10]
 ),
 (
 inputA: [-3.2, -3.2, -2.4, 7, -10.1],
 inputB: [100, -3.2, 2.4, -7, -10.1],
 expected: [100, -6.4, 2.4, 7, -20.2]
 ),
]
for (caseNumber, testcase) in testcases.enumerated() {
 let actual = f(testcase.inputA, testcase.inputB)
 assert(actual == testcase.expected,
 "Testcase #\(caseNumber) \((testcase.inputA, testcase.inputB)) failed. Got \(actual), but expected \(testcase.expected)!")
 print("Testcase #\(caseNumber) passed!")
}

Answer 6

Stax, 8 bytes

Ç√'81⁄2B=☺

Run and debug it

Answer 7

Desmos, 26 bytes

f(a,b)=\{a=b:2a,a>b:a,b\}

Leading newline necessary.

Try it on Desmos!

• naffetS: In your TIO link, you might want to give an example giving it lists instead of numbers, like so: desmos.com/calculator/iil8pysjzu
• fad: @Steffan L1 and L2 are lists, they’re just defined through the table’s first two columns, and then the third column shows f(L1, L2) which is the result of passing the function the two lists. Desmos isn’t evaluating it row by row as it may initially seem

Answer 8

Python, (削除) 57 (削除ここまで) 56 bytes

lambda a,b:[x==y and x+y or max(x,y)for x,y in zip(a,b)]

Generators, (削除) 57 (削除ここまで) 56 bytes

lambda a,b:(x==y and x+y or max(x,y)for x,y in zip(a,b))

-1 each by Steffan

• naffetS: -1 byte using and and or: Try it online!
• Eric Xue: Thanks a lot! I used it on my lists and generators solutions.

Answer 9

BQN, (削除) 6 (削除ここまで) 5 bytes

-1 byte by porting emanresu A's Vyxal answer

×ばつ1+=

Anonymous tacit function that takes equal-length lists as left and right arguments. Try it at BQN online!

Explanation

×ばつ1+=
 = Compare the two lists itemwise (1 for equal, 0 for not equal)
 1+ Add 1 to each (2 for equal, 1 for not equal)
⌈ Get the itemwise maximums of the two lists
 ×ばつ Multiply (itemwise)

Original solution

The spec can be implemented very literally in 6 bytes:

=◶⌈‿+ ̈
 ̈ Apply this function to corresponding pairs of elements from the arguments:
= Test if the elements are equal (1 if so, 0 if not)
 ◶ Use that result to pick a function from this list and apply it:
 ⌈ If 0 (not equal), then max
 ‿+ If 1 (equal), then add

• emanresu A: Turns out I unintentionally ported the Jelly/APL answers lol.
• DLosc: Ha--and the APL answer is actually identical to this one!

Answer 10

Factor, 36 bytes

[ [ 2dup = [ + ] [ max ] if ] 2map ]

Try it online!

Answer 11

POSIX Shell + Utilities, 40 bytes

paste $@|awk '0ドル=1ドル<2ドル?2ドル:1ドル>2ドル?1ドル:2*1ドル'

"Arrays" defined as "text files per POSIX".
Obviously buggy insofar as [0], [0] -> []. Doesn't come up in the validator, so. Append the 2-byte "" sequence to also handle that edge case.

Transcript of test cases:

$ cat cg; echo; wc -c cg
paste $@|awk '0ドル=1ドル<2ドル?2ドル:1ドル>2ドル?1ドル:2*1ドル'
40 cg
$ ./cg /dev/null /dev/null
$ ./cg <(printf '%s\n' 1 2 3) <(printf '%s\n' 1 3 2)
2
3
3
$ ./cg <(printf '%s\n' 1 3 3.2 2.3) <(printf '%s\n' 3 1 3.2 2.6)
3
3
6.4
2.6
$ ./cg <(printf '%s\n' 1 2 3 4 5 5 7 8 9 10) <(printf '%s\n' 10 9 8 7 6 5 4 3 2 1)
10
9
8
7
6
10
7
8
9
10
$ ./cg <(printf '%s\n' -3.2 -3.2 -2.4 7 -10.1) <(printf '%s\n' 100 -3.2 2.4 -7 -10.1)
100
-6.4
2.4
7
-20.2

Answer 12

CJam, 16 bytes

{.{a+_:e>\:=)*}}

Try it online!

Oh hey look, my code is cute :=) but a big dude \:=)*

Answer 13

Clojure, 40 bytes

#(map(fn[x y]((if(= x y)+ max)x y))% %2)

Try it online!

Answer 14

PHP, 74 bytes

function($a,$b){foreach($a as$i=>$p)echo$p*($p>=$q=$b[$i])+$q*($q>=$p),_;}

Prints the results separated by an underscore. Try it online.

Answer 15

Swift, 80 bytes

var o = [Int]();for (c, d) in zip(a,b){o.append(c==d ? c*2 : max(c,d))};return o

• Create the output array
• zip together a & b
• for each loop through with c & d
• append result to output array
• return output array

• Cyoce: You should be able to remove most of those spaces.
• Alexander: I got a 41 byte swift answer, check it out: codegolf.stackexchange.com/a/143367/11490

Answer 16

MY, 20 bytes

αωD6ǵ'69ǵ';ƒ⇹(αω=×ばつ↵

Try it online!

This uses the exact same approach as my APL and Jelly answers, except MY doesn't have some of the builtins:

• D6ǵ'69ǵ';ƒ, this pushes <SPACE>⍐ in MY's codepage (where <SPACE> is a physical space) as a function, which turns two items into a list, then finds the maximum.
• ⇹(, map over each argument, then apply the function.

Answer 17

K, 12 bytes

{x|y*(1+x=y)}

Exact same strategy as my other answers.

Try it online!

Any golfing tips are welcome, as I don't really know K.

Answer 18

Erlang, 65 bytes

fun(A,B)->lists:zipwith(fun(C,C)->C+C;(D,E)->max(D,E)end,A,B)end

example:

1> (fun(A,B)->lists:zipwith(fun(C,C)->C+C;(D,E)->max(D,E)end,A,B)end)([1, 3, 3.2, 2.3], [3, 1, 3.2, 2.6] ).
[3,3,6.4,2.6]

just a straightforward anonymous fun

Answer 19

Jq 1.5, (削除) 49 (削除ここまで) 44 bytes

transpose|map(if.0==.1then add else max end)

Sample input

[[], []]
[[1, 2, 3], [1, 3, 2]]
[[1, 3, 3.2, 2.3], [3, 1, 3.2, 2.6]]
[[1,2,3,4,5,5,7,8,9,10], [10,9,8,7,6,5,4,3,2,1]]
[[-3.2, -3.2, -2.4, 7, -10.1], [100, -3.2, 2.4, -7, -10.1]]

Sample run

$ jq -Mc 'transpose|map(if.0==.1then add else max end)' input
[]
[2,3,3]
[3,3,6.4,2.6]
[10,9,8,7,6,10,7,8,9,10]
[100,-6.4,2.4,7,-20.2]

Character count

$ echo -n 'transpose|map(if.0==.1then add else max end)' | wc -c
 44

Thanks again to Jonathan Frech for helping eliminate 5 bytes!

• Jonathan Frech: Is the space in .[1] then not omittable?
• Jonathan Frech: 44 bytes: transpose|map(if.0==.1then add else max end).

Answer 20

Perl 5, 59 + 1 (-p) = 60 bytes

say join$",map$_>($t=$F[$i++])?$_:$_<$t?$t:$_*2,split/ /,<>

Try it online!

Answer 21

SmileBASIC, 120 bytes

An answer using ONLY the ARYOP function.

DEF B A,B,L
DIM C[L],D%[L]ARYOP 6,C,A,A,B
ARYOP.,A,A,B
ARYOP 1,B,A,C
ARYOP 1,B,C,B
ARYOP 6,D%,B,-1,0ARYOP 4,A,C,D%,A
END

Function is called as B array1 , array2 , length. Output is stored in array1.

Explanation:

'get minimum, sum, and maximum of B and A
ARYOP #AOPCLP,C,A,A,B 'c=clamp(a,a,b) (gets the minimum of a and b)
ARYOP #AOPADD,A,A,B 'a=a+b (get the sum)
ARYOP #AOPSUB,B,A,C 'b=a-c (get the maximum)
'check if min==max
ARYOP #AOPSUB,B,C,B 'b=c-c (min-max, will be negative or 0)
ARYOP #AOPCLP,D%,B,-1,0 'd%=clamp(b,-1,0) (d% is an integer array. 0=equal, -1=not equal)
'add subtract min from sum if elements were not equal
ARYOP #AOPMAD,A,C,D%,A 'a=c*d%+a

This challenge seemed boring at first, but there are actually a lot of different ways to do it. For example:

-calculate the maximum, add the minimum if B==A

-calculate the sum, subtract A if A<B, subtract B if B<A

-b+max(a-b,0)+a*(a==b)

Answer 22

Tcl, 57 bytes

proc M A\ B {lmap a $A b $B {expr $a-$b?max($a,$b):2*$a}}

Try it online!

Answer 23

APL(Dyalog Unicode), ^{(削除) (削除ここまで)}15 bytes ^SBCS

(×ばつ1+⊣=⊢)/ ̈, ̈

Try it on APLgolf!

Can be golfed as:

((×ばつ1+=)/ ̈, ̈)×ばつ1+=

So it ends up being the same as the other APL answer...

Answer 24

J-uby, 31 bytes

Accidental port of ymbirtt's Ruby answer.

:zip|:*&:[]%[-[+:+,:max],+:<=>]

Attempt This Online!