Sum the array times n, except the last

Question

I've been posting relatively hard challenges recently, so here goes an easy one.

Task

Given an array \$A\$ and a number \$n\$, calculate the sum of all numbers of \$A\$ multiplied by \$n\$, except the last one. All numbers (the elements of \$A\$ and the value of \$n\$) are positive integers, and \$A\$ is non-empty. Shortest code in bytes wins.

I have a 3-byte J solution. Can you find it (or beat it in a different language)?

Test cases

A           N   Ans   Explanation
3 1 4 1 5   10  95    (3+1+4+1)*10+5
3 1 4 1 5   1   14    (3+1+4+1)*1+5
1           999 1     1

\$\begingroup\$ Can we take the list in reverse? \$\endgroup\$
– user92069
Jul 11, 2020 at 8:20 — user92069, Jul 11, 2020 at 8:20
\$\begingroup\$ @Third-party'Chef' No. \$\endgroup\$
– Bubbler
Jul 11, 2020 at 8:26 — Bubbler, Jul 11, 2020 at 8:26
\$\begingroup\$ I wonder if your J solution used mixed base conversion \$\endgroup\$
– xnor
Jul 11, 2020 at 9:37 — xnor, Jul 11, 2020 at 9:37
\$\begingroup\$ Can we take the input as numbers instead of a single array? \$\endgroup\$
– TwilightSparkle
Jul 11, 2020 at 9:54 — TwilightSparkle, Jul 11, 2020 at 9:54
\$\begingroup\$ @HighlyRadioactive Yes, that's fine. \$\endgroup\$
– Bubbler
Jul 11, 2020 at 12:19 — Bubbler, Jul 11, 2020 at 12:19

Giuseppe · Accepted Answer · 2022-02-04 17:47:15Z

2

tinylisp, 58 bytes

(load library
(d S(q((A N)(i(t A)(a(*(h A)N)(S(t A)N))(h A

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tinylisp, 78 65 bytes

(d S(q((A N)(i(t A)(i(h A)(a(S(c(s(h A)1)(t A))N)N)(S(t A)N))(h A

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Solution without using library, which is only for *.

-13 bytes thanks to DLosc

edited Feb 4, 2022 at 17:47

answered Feb 4, 2022 at 16:16

Giuseppe

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1

\$\begingroup\$ The non-library version can be 65 bytes if you make the multiplication algorithm part of the main function. \$\endgroup\$
– DLosc
Feb 4, 2022 at 16:28
\$\begingroup\$ @DLosc that's incredibly clever. I have a lot of practice to do! \$\endgroup\$
– Giuseppe
Feb 4, 2022 at 17:47

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Rydwolf Programs · Accepted Answer · 2022-02-18 21:31:37Z

2

Risky, 9 bytes

-_{1+0+00_?+0+?*?

Try it online!

edited Feb 18, 2022 at 21:31

Rydwolf Programs

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answered Jul 24, 2021 at 21:52

xigoi

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Peter · Accepted Answer · 2023-01-18 18:26:23Z

2

C (gcc), 56 bytes

s,i;f(v,l,f)int*v;{for(i=0;i<l-1;s+=v[i++]);return s*f;}

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f takes a vector (v), the length of the vector (l) and the factor to multiply the vector with (f) as arguments. It sums up the values in the vector, except for the last one (in s) and returns the sum multiplied by the factor.

answered Jan 18 at 18:26

Peter

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GammaFunction · Accepted Answer · 2020-07-11 21:59:25Z

1

Zsh, 25 bytes

n=`<&0`
<<<$[0${@/#/*n+}]

Try it online!

Takes the list as arguments and N on stdin. Inspired by the JS answer. Prefix each element with *n+ and $[evaluate arithmetically]. We have to add a 0 to the start as well. This is one byte shorter than using the join flag <<<$[${(j:*n+:)@}]

Zsh `-P`, 24 bytes

a=(0 \*`<&0`+$@)
<<<$[a]

Try it online!

Alternate solution using the -P flag, which enables RC_EXPAND_PARAM to do the same thing.

edited Jul 11, 2020 at 21:59

answered Jul 11, 2020 at 21:48

GammaFunction

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Jhal · Accepted Answer · 2020-07-11 22:10:17Z

1

Vimscript 36 Bytes

Disgusted to report that Arnauld's solution also works for vimscript.

let F={a,n->eval(join(a,"*".n."+"))}

answered Jul 11, 2020 at 22:10

Jhal

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640KB · Accepted Answer · 2020-07-12 17:11:09Z

1

PHP, 41 bytes

fn($a,$n)=>array_pop($a)+array_sum($a)*$n

Try it online!

Just trying to use all the built-ins!

answered Jul 12, 2020 at 17:11

640KB

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t-clausen.dk · Accepted Answer · 2020-07-13 09:01:49Z

1

T-SQL, 40 bytes

I am using a table instead of an array, sql doesn't have arrays

The test uses a temporary table instead of a real table, because of lack of permissions to create a table.

SELECT sum(a*@-i/@@rowcount*a*~-@)FROM t

Try it online

edited Jul 13, 2020 at 9:01

answered Jul 13, 2020 at 8:45

t-clausen.dk

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Ismael Miguel · Accepted Answer · 2020-07-13 09:03:25Z

SimpleTemplate, 81 bytes

It's fairly chunky :/
Mostly due to limitations in my language...

{@eachargv.0}{@ifloop.last is equal0}{@set*_ _,argv.1}{@/}{@incby_ R}{@/}{@echoR}

Takes a string of numbers or an array as the first argument, and the n as the 2nd argument.

You can try this on http://sandbox.onlinephpfunctions.com/code/4c7290781560c876ff1e72e5d1680ed7b98861a3

Ungolfed:

The code above is a little weird to read...

Here's a more readable version:

{@set result 0}
{@each argv.0 as number}
    {@if loop.last is equal to false}
        {@set* number number, argv.1}
    {@/}
    {@inc by number result}
{@/}
{@echo result}

Notes:

{@set result 0} is optional, as {@inc} will create the variable, if it doesn't exist
{@each argv.0 as number} doesn't need need the as number, defaulting to the variable _ to store values
{@if loop.last is equal to false} uses the special variable loop to know if it is the last item in the {@each} Also, false is the same as 0.
{@set* number number, argv.1} multiplies number with argv.1 and stores it inside number. If number was an array, it would multiply with all the values.
{@inc by number result} will increment the variable result by number (effectivelly, result = result + number)
{@/} is usually optional, but, with this code, they are all required.

msh210 · Accepted Answer · 2020-07-15 12:23:00Z

1

Perl 5 + `-pi`, 19 bytes

s/,/*$^I+/g;$_=eval

For example, for multiplicand 10, perl -pi10 -e's/,/*$^I+/g;$_=eval

Try it online. Idea stolen from this J answer. Accuracy improved by Dom Hastings in comments on this answer (many thanks!).

edited Jul 15, 2020 at 12:23

answered Jul 14, 2020 at 12:20

msh210

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\$\begingroup\$ You need to take n from input too, it's not always 10! :) \$\endgroup\$
– Dom Hastings
Jul 15, 2020 at 12:12
\$\begingroup\$ You can get the same byte-count using non-standard input for n (-i): Try it online! \$\endgroup\$
– Dom Hastings
Jul 15, 2020 at 12:15

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Sandra · Accepted Answer · 2020-07-15 16:14:58Z

1

dc, 21 bytes

ss0[+z2<o]dso0rx*ls+p

Examples:

dc -e '10 3 1 4 1 5 ss0[+z2<o]dso0rx*ls+p'
95
dc -e '1 3 1 4 1 5 ss0[+z2<o]dso0rx*ls+p'
14
dc -e '999 1 ss0[+z2<o]dso0rx*ls+p'
1

answered Jul 15, 2020 at 16:14

Sandra

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Jo King · Accepted Answer · 2020-07-16 08:08:19Z

1

Raku, 21 bytes

{*.join("*$_+").EVAL}

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This works the same as the Perl 5 answer and also works with non-mutable lists, unlike the existing Raku answer, which is only one byte smaller than this.

Note: My previous answer of the same size does not work for singleton lists, which I've lodged an issue about.

edited Jul 16, 2020 at 8:08

answered Jul 16, 2020 at 1:11

Jo King♦

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Conor James Thomas Warford Hen · Accepted Answer · 2020-07-21 18:22:27Z

1

excel, 25 bytes

Enter A followed by n in one column, followed by this formula

=SUM(R1:R[-3])*R[-1]+R[-2]

answered Jul 21, 2020 at 18:22

Conor James Thomas Warford Hen

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1

\$\begingroup\$ Note: R1C1 Reference Style option must be checked. \$\endgroup\$
– General Grievance
Jul 22, 2020 at 18:59

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val is still with Monica · Accepted Answer · 2020-07-22 18:53:23Z

1

Lua, 58 bytes

r,t=0,{...}for i=2,#t-1 do
r=r+t[i]end print(r*t[1]+t[#t])

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Having almost no array functions, Lua doesn't do too well in this challenge.

answered Jul 22, 2020 at 18:53

val is still with Monica

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user · Accepted Answer · 2020-07-23 15:56:23Z

1

Scala, 22 bytes

a=>a.last+_*a.init.sum

This returns a List[Int] => Int => Int

Try it online

answered Jul 23, 2020 at 15:56

user

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Mukundan314 · Accepted Answer · 2020-07-31 15:11:16Z

1

MATL, 9 bytes

*1G0)0Z(s

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Explanation

*1G0)0Z(s
*          % Multiply the inputs and push it onto the stack
 1G        % Push first input onto the stack
   0)      % Replace top stack element with its last element
     0Z(   % Set last element of multiplied inputs to top element in stack
        s  % Replace top stack element with its sum

answered Jul 31, 2020 at 15:11

Mukundan314

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att · Accepted Answer · 2020-07-31 17:28:30Z

1

Wolfram Language (Mathematica), 16 bytes

a___~f~b_=+a#+b&

Try it online!

This one doesn't need a strange-looking input.

Takes input as f[A][n].

older, 17 bytes

#//.a_@b_:>a#2+b&

Try it online!

Takes a singly linked list as input: if X is a value and L is a list, X is the single-element list with element X, and X[L] is the list with element X, followed by the elements of L. For example, 3@1@4@1@5=3[1[4[1[5]]]] is the list with 3, 1, 4, 1, 5.

Per this discussion, we can take the first element with Head, and the tail with Last.

edited Jul 31, 2020 at 17:28

answered Jul 11, 2020 at 21:47

att

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\$\begingroup\$ is {3@1@4@1@5,10} a valid input? If it is, nice job! I tried something similar but the best I could do was 24 bytes #/.{a__,b_}:>Tr@{a}#2+b& \$\endgroup\$
– ZaMoC
Jul 11, 2020 at 23:20
\$\begingroup\$ @J42161217 a flat input can get down to 18 byes by taking it in Dot or a Flat two-byte operator (a_.b_ is Times[Optional[a_],b_] rather than Dot[a_,b_]): Try it online! For a list, you can get 20: #/.{a__,b_}:>+a#2+b& \$\endgroup\$
– att
Jul 11, 2020 at 23:57

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TehPers · Accepted Answer · 2020-07-31 20:12:11Z

1

Rust, 45 bytes

|a,n|a.pop().unwrap()+a.iter().sum::<i64>()*n

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The expected argument types are a: &mut Vec<i64> and n: i64.

answered Jul 31, 2020 at 20:12

TehPers

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Neil · Accepted Answer · 2020-11-19 11:15:58Z

Charcoal, 10 9 bytes

Ｉ⁺⊟θ×η↨θ¹

Try it online! Link is to verbose version of code. Presumably Charcoal has the same problem as IO when it comes to summing empty lists. Edit: saved 1 byte by converting from base 1 instead. Explanation:

   θ        `A`
  ⊟         Remove last element
 ⁺          Added to
       θ    Remaining elements of `A`
      ↨ ¹   Take the sum by converting from base 1
    ×       Multiplied by
     η      `n`
Ｉ           Cast to string
            Implicitly print

Shaggy · Accepted Answer · 2020-11-19 11:48:22Z

1

Japt `-h`, 6 bytes

Ç+Ux*V

Try it

answered Nov 19, 2020 at 11:48

Shaggy

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Julian · Accepted Answer · 2020-11-20 03:35:22Z

1

PowerShell Core, 29 bytes

param($a,$b)$a-join"*$b+"|iex

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^ inspired by Arnauld's solution

My original one

PowerShell Core, 75 bytes

param($a,$b)(($a[($l=$a.Length-1)]+$b*($a[0..($l-1)]-join'+'|iex)),$a)[!$l]

Try it online!

edited Nov 20, 2020 at 3:35

answered Nov 20, 2020 at 3:30

Julian

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Razetime · Accepted Answer · 2021-02-24 06:28:14Z

1

Stax, ⁶ 4 bytes

╡÷E@

Run and debug it

edited Feb 24, 2021 at 6:28

answered Nov 20, 2020 at 5:20

Razetime

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chunes · Accepted Answer · 2021-06-02 03:43:28Z

1

Factor + `math.unicode`, 23 bytes

[ dup pop -rot Σ * + ]

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answered Jun 2, 2021 at 3:43

chunes

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Wasif · Accepted Answer · 2021-06-02 04:18:09Z

1

Vyxal `s`, 5 bytes

*ṫ⁰/J

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answered Jun 2, 2021 at 4:18

Wasif

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cnamejj · Accepted Answer · 2022-02-19 08:10:11Z

Ly, 18 bytes

&n&spp&+>l<s>l*+u;

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&n                 - read all the numbers into the stack
  &s               - save the entire stack to the backup cell
    pp             - delete top two entries on the stack
      &+           - sum the stack
        >l         - switch to clean stack, load original input
          <s       - switch back, save summary to backup cell
            >l     - switch stacks, load save sum of 2nd to N entries
              *    - multiple top two entries on stack
               +   - add top two stack entries
                u  - print top of stack as a number
                 ; - exit the code to avoid printing the rest of the stack

chunes · Accepted Answer · 2023-01-18 10:11:33Z

1

Arturo, 28 bytes

$[a,n][+last a n*sum chop a]

Try it

$[a,n][           ; a function taking args a and n
  +last a         ; add the last elt in a to
  n*sum chop a    ; n times the sum of a without its last elt
]                 ; end function

answered Jan 18 at 10:11

chunes

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score 0 · Accepted Answer · 2020-07-13 07:19:56Z

Io, 31 bytes

Saves a byte over the 32 byte solution. But it's boring.

method(a,N,a sum*N-a pop*(N-1))

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Explanation

method(a, N,
    a sum * N         // Sum the input, multiply by N
  - a pop * (N - 1)   // Minus the last item, multiplied by N - 1
)

Io, 32 bytes

Just as comparison

method(a,N,a push(a pop/N)sum*N)

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Explanation

method(a, N,
           a pop           // Extract the last item from the input list
                /N         // Divide it by N
    a push(       )        // And then put it back into the original list
                   sum     // Sum the list
                      *N   // Multiply the value by N
)

kaadmy · Accepted Answer · 2020-08-01 16:51:40Z

0

C (gcc), 53 bytes

Saved 2 bytes thanks to ceilingcat

s;f(a,n)int*a,n;{for(s=0;a[1];s+=*a++);return*a+s*n;}

Try it online!

edited Aug 1, 2020 at 16:51

answered Jul 31, 2020 at 16:10

kaadmy

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sugarfi · Accepted Answer · 2020-08-04 04:03:44Z

0

Perl 6, 29 bytes

->$a,$b {$a.pop+([+] $a)*$b};

Try it online!

answered Aug 4, 2020 at 4:03

sugarfi

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\$\begingroup\$ You can use $^a and $^b instead, as well as .sum, and the semi-colon is not needed, which ends up being the same as a previous Raku answer \$\endgroup\$
– Jo King ♦
Aug 4, 2020 at 6:14
\$\begingroup\$ @JoKing Oh, my bad! Thanks for the tip, though - I'm still learning Raku. \$\endgroup\$
– sugarfi
Aug 4, 2020 at 16:31

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orangey · Accepted Answer · 2021-07-25 20:19:39Z

TI-BASIC, 30 bytes (on-calc) / 37 bytes (as text)

Assumes list variable L₁ contains the array and variable N contains n.

dim(L₁
Nsum(L₁,1,Ans-1)+L₁(Ans

Explanation

dim(L₁: Get the size of L₁, to be used in the next line as Ans.
Nsum(L₁,1,Ans-1)+L₁(Ans: The sum( function has optional arguments to specify the beginning and end of a region of the list to be summed. The sum is implicitly multiplied by N, then added to the last element of the list, and implicitly printed.

Closing parentheses can be left out at the end of lines in TI-BASIC.

Sum the array times n, except the last

Task

Test cases

59 Answers 59

tinylisp, 58 bytes

tinylisp, 78 65 bytes

Risky, 9 bytes

C (gcc), 56 bytes

Zsh, 25 bytes

Zsh -P, 24 bytes

Vimscript 36 Bytes

PHP, 41 bytes

T-SQL, 40 bytes

SimpleTemplate, 81 bytes

Perl 5 + -pi, 19 bytes

dc, 21 bytes

Raku, 21 bytes

excel, 25 bytes

Lua, 58 bytes

Scala, 22 bytes

MATL, 9 bytes

Explanation

Wolfram Language (Mathematica), 16 bytes

Rust, 45 bytes

Charcoal, 10 9 bytes

Japt -h, 6 bytes

PowerShell Core, 29 bytes

PowerShell Core, 75 bytes

Stax, 6 4 bytes

Factor + math.unicode, 23 bytes

Vyxal s, 5 bytes

Ly, 18 bytes

Arturo, 28 bytes

Io, 31 bytes

Explanation

Io, 32 bytes

Explanation

C (gcc), 53 bytes

Perl 6, 29 bytes

TI-BASIC, 30 bytes (on-calc) / 37 bytes (as text)

Explanation

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