Triangle Area Side Side Side

Question

Given three sides of a triangle, print area of this triangle.

Test cases:

In: 2,3,4

Out: 2.90473750965556

In: 3,4,5

Out: 6

Assume the three side a,b,c always a>0,b>0,c>0,a+b>c,b+c>a,c+a>b.

Answer 1

J, 23 19 chars

   (4%~2%:[:*/+/-0,+:)

   (4%~2%:[:*/+/-0,+:) 2 3 4
2.90474

   (4%~2%:[:*/+/-0,+:) 3,4,5
6

17-char version if input is in i: 4%~%:*/(+/,+/-+:)i

original 23-char version: (%:@(+/**/@(+/-+:))%4:)

Answer 2

APL 21 20

Takes screen input via ←⎕

(×/(+/t÷2)-0,t←⎕)*.5

Answer 3

Mathematica 23

√Times@@(+##/2-{0,##})&

Answer 4

Python 2, 53

t=input()
s=a=sum(t)/2.
for x in t:a*=s-x
print a**.5

Input: 2,3,4

Output: 2.90473750966

Answer 5

Python 57 bytes

a,b,c=input()
s=(a+b+c)*.5
print(s*(s-a)*(s-b)*(s-c))**.5

Using Heron's Formula.

Sample usage:

$ echo 2,3,4 | python triangle-area.py
2.90473750966

$ echo 3,4,5 | python triangle-area.py
6.0

---

A 58 byte variant:

a,b,c=input()
print((a+b+c)*(b+c-a)*(a+c-b)*(a+b-c))**.5/4

Answer 6

GolfScript, 38 characters

~].~++:d\{2*d\-*}/'"#{'\+'**0.5/4}"'+~

Since the question didn't specify otherwise I chose to work only on integer lengths. Sides must be given on STDIN separated by spaces.

Example:

> 2 3 4
2.9047375096555625

Answer 7

R : 48 43 characters

f=function(...)prod(sum(...)/2-c(0,...))^.5

Using Heron's formula as well but taking advantage of R's vectorization.
Thanks to @flodel for the idea of the ellipsis.

Usage:

f(2,3,4)
[1] 2.904738
f(3,4,5)
[1] 6

Answer 8

APL, 23 20 characters

{(×/(+/⍵÷2)-0,⍵)*÷2} 2 3 4

Example:

> {(×/(+/⍵÷2)-0,⍵)*÷2} 2 3 4
2.90474

Answer 9

K, 23

{sqrt s**/(s:.5*+/x)-x}

Example

k){sqrt s**/(s:.5*+/x)-x} 2 3 4
2.904738

Answer 10

Javascript, 88 85

v=prompt().split(/,/g);s=v[0]/2+v[1]/2+v[2]/2;Math.sqrt(s*(s-v[0])*(s-v[1])*(s-v[2]))

Not good but fun :) Also Heron... Demonstrates the ungolfability of simple problems in JS lol

Note: run from console to see result.

88->85: Removed a, b and c.

Answer 11

Mathematica 20 16 or 22 18 bytes

With 4 bytes saved by @swish.

This returns an exact answer:

Area@SSSTriangle@

Example

Area@SSSTriangle[2,3,4]

---

To return the answer in decimal form, two additional bytes are required.

N@Area@SSSTriangle[2,3,4]

2.90474

Answer 12

PHP, 78 77

<?=sqrt(($s=array_sum($c=fgetcsv(STDIN))/2)*($s-$c[0])*($s-$c[1])*$s-=$c[2]);

Useage:

php triangle.php
2,3,4

Output: 2.9047375096556

I don't think I can make it shorter? I'm still new to golfing. Anyone let me know if I overlooked something.

Thanks Primo for saving me 1 byte, lol.

Answer 13

Haskell: 51 (27) characters

readLn>>=(\l->print$sqrt$product$map(sum l/2-)$0:l)

A very straight-forward implementation of Heron's formula. Example run:

Prelude> readLn>>=(\l->print$sqrt$product$map(sum l/2-)$0:l)
[2,3,4]
2.9047375096555625
Prelude>

Note that it accepts any numeric input, not only integers. And if the input already is in l the solution only needs to be 36 characters long, and if we are not interested in printing the answer the solution only needs to be 30 characters long. What more is that if we can allow ourself to change the input format we can remove 3 more characters. So if our input looks like [2,3,4,0.0] and is already in l we can get our answer with only:

sqrt$product$map(sum l/2-)l

Example run:

Prelude> let l = [2,3,4,0.0]
Prelude> sqrt$product$map(sum l/2-)l
2.9047375096555625
Prelude>

Answer 14

JavaScript (84 86)

s=(eval('abc '.split('').join('=prompt()|0;'))+a+b)/2;Math.sqrt(s*(s-a)*(s-b)*(s-c))

Another JavaScript solution based on Heron's formula, but trying a different approach for loading variables. Needs to be run from the console. Each side is entered in a separate prompt.

EDIT: Make use of return value of eval to save 2 characters. Beats @tomsmeding, wahoo! :)

Answer 15

Tcl, 74 chars.

proc R {a b c} {set s ($a+$b+$c)/2.
expr sqrt($s*($s-$a)*($s-$b)*($s-$c))}

Pass the sides as argument.

For the input 2 3 4 the value of s is (2+3+4)/2. as string. Double evaluation FTW.

Answer 16

Japt, 17 16 15 bytes

½*Nx
NmnU ×*U q

Test it

Saved 2 bytes thanks to ETH pointing out a redundant newline and some alternative ways to reduce the array.

Answer 17

Excel, 42 bytes

Based on Heron's formula, high school algebra to golf.

=SQRT(((A1+B1)^2-C1^2)*(C1^2-(A1-B1)^2))/4

Ungolfed / Unalgebra'ed

=SQRT((A1+B1+C1)/2*(((A1+B1+C1)/2)-A1)*(((A1+B1+C1)/2)-B1)*(((A1+B1+C1)/2)-C1))

Answer 18

Julia 0.6.0, 48 bytes

Basically heron's formula:

f(a,b,c)=(p=(a+b+c)/2;sqrt(p*(p-a)*(p-b)*(p-c)))

Answer 19

dc, 34 bytes

9ksssddlsld++2/d3R-rdls-rdld-***vp

Try it online!

Answer 20

C (gcc), 55 bytes

#define f(a,b,c)sqrt((a+b+c)*(a+b-c)*(a-b+c)*(b+c-a))/4

Try it online!

Yet another implementation of Hero's formula.

Answer 21

TI-BASIC, 14 12 bytes

4⁻¹√(sum(Ansprod(sum(Ans)-2Ans

Starting from a Heron's Formula routine written by Kenneth Hammond (Weregoose), I golfed off two bytes. Note that TI-BASIC is tokenized, and each token, like Ans and prod(, is one or two bytes in the calculator's memory.

Input through Ans i.e. in the form {a,b,c}:[program name].

Explained:

                   sum(Ans)-2*Ans   (a+b+c)-2{a,b,c}={b+c-a,c+a-b,a+b-c}
          Ans*prod(                 {a,b,c}*(b+c-a)(c+a-b)(a+b-c)
      sum(                          (a+b+c)(b+c-a)(c+a-b)(a+b-c)
4⁻¹*√(                              √((a+b+c)(b+c-a)(c+a-b)(a+b-c)/16)
                                    =√(s(s-a)(s-b)(s-c))

Answer 22

#include<stdio.h>
#include<math.h>
main()
{
  double a,b,c,s,area;
  scanf("%d %d %d" &a,&b,&c);
  s=sqrt((a*a)+(b*b)+(c*c));
  area=[sqrt(s*(s-a)*(s-b)*(s-c))]/2;
}

Answer 23

ARBLE, 36 bytes

sqrt(a*(a-b)*(a-c)*(a-d))((b+c+d)/2)

Heron's formula.

Try it online!

Answer 24

Perl 5 -MList::Util=sum -ap, 40 bytes

$r=$t=.5*sum@F;map$r*=$t-$_,@F;$_=sqrt$r

Try it online!

Answer 25

Stax, 10 bytes

╝0∞♀»♦▓y╩╪

Run and debug it

Operates triples of floating point numbers. Uses Heron's Formula

Answer 26

APL(NARS), 16 chars, 32 bytes

{√×/(+/⍵÷2)-0,⍵}

One has to cenvert the Erone formula if a, b, c are sides of triangle

p   =(a+b+c)/2 
Area=√p*(p-a)(p-b)(p-c)

to APL language... test

  f←{√×/(+/⍵÷2)-0,⍵}
  f 2 3 4
2.90473751
  f 3 4 5
6