Square of the number of ones

Question

I'm solving problem: in file "a.in" given the number N - length of the number consists of ones. Need to gets square of it, and put this in file "a.out". This is my shortest solution(150 bytes):

char s[1<<27];j;main(i,n){for(fscanf(fopen("a.in","r"),"%d",&n),i=n*=2;--i;j+=i<n/2?i:n-i,s[i-1]=48+j%10,j/=10);fprintf(fopen("a.out","w"),"%s\n",s);}

This is formated copy:

char s[1<<27];j;
main(i,n){
    for(fscanf(fopen("a.in","r"),"%d",&n),i=n*=2;--i;
        j+=i < n/2 ? i: n-i,
        s[i - 1] = 48 + j % 10,
        j /= 10
    );
    fprintf(fopen("a.out","w"),"%s\n",s);
}

The best solution of this problem has size 131 bytes, how? Valid languages: C, C#, C++, Pascal, Java.

Answer 1

without changing your logic, you can save 9 characters by using fputs (instead of fprintf).

fputs(s,fopen("a.out","w"));

you can also save one character by not doubling n at first step, thus removing divide by two:

...,i=n*2;--i;
j+=i<n?i:2*n-i

Answer 2

You can save another character, by doing j/=10 after for - for(...)j/=10;

My best so far, 145 characters:

char s[1<<27];j;
main(i,n){
    for(fscanf(fopen("a.in","r"),"%d",&n),s[i=n*2-1]=10;i;
        j+=i<n?i:n*2-i,
        s[--i]=48+j%10
    )j/=10;
    fputs(s,fopen("a.out","w"));
}

Answer 3

C, 104 chars

(Assuming ugoren's comment is correct)

main(n,k){fscanf(fopen("a.in","r"),"%d",&n);for(k=1;--n;k=k*10+1);fprintf(fopen("a.out","w"),"%d",k*k);}

Note that I needed to compile it with -m32 on OSX to keep it from crashing. Probably something to do with the implicit prototypes brought about by not including stdio.h.

Answer 4

J, 17 characters

Invalid answer and not really of any use to the OP, but I was bored and this occupied a few minutes.

*:10#.1$~".1!:1[1

1!:1[1 take input from the keyboard,

1$~ creates a list of 1s of the length specified by the input,

10#. converts to a base 10 number,

*: squares it.

Answer 5

GolfScript 7

Another answer in an illegal language, for the same reason as the one invoked by Gareth.

~1`*~.*

Explanation:

• takes a number as command line parameter
• ~ evaluates the number
• 1` pushes the '1' string on the stack
• * multiplies the character '1' by the number specified as input (results in a string)
• ~ evaluates the string of 1s, thus storing the equivalent numeric value on the stack
• .* squares the existing value

In order to get the expected output, the program should be called like this:

 more a.in | ruby golfscript.rb program.gs > a.out # :-)

Answer 6

Jelly, 4 bytes (feedback welcome!)

1xV²

Try it online!

Repeat '1' a number of times equal to the input (x), concatenate and eValuate the result, and square it.

Old solution:

RŒBV

Try it online!

As per @ugoren's explanation. Make a range from 1 to N, then bounce it (mirror except the last element) with ŒB and use V to concatenate the digits.

Answer 7

Wren, 55 bytes

Just do an invalid answer in case file manipulation doesn't work.

Fn.new{|x|Num.fromString("1"*Num.fromString(x)).pow(2)}

Try it online!

Explanation

Takes input as string:

Fn.new{|x|                                            } // New anonymous function
                             Num.fromString(x)          // Convert input into a number
          Num.fromString("1"*                 )         // Evaluate 1 with that number times
                                               .pow(2)  // Square the resulting value

Answer 8

Just for fun a 'dc' solution. It read/writes from stdin/stdout, because of its limitations

$ dc -e '?0sn[lnA*1+sn1-d0<x]dsxxlnd*p' <<< 3
12321

Answer 9

Keg, -hr, 5 bytes

1⅍*ℤ²

Try it online!

Another illegal answer, but hey, as far as I know, there ain't any CGCC jail y'all can throw me into.

Answer 10

C#, 172 chars

namespace System{class P{static void Main(){var b=Numerics.BigInteger.Parse(new String('1',int.Parse(IO.File.ReadAllText("a.in"))));IO.File.WriteAllText("a.out",b*b+"");}}}

Best I could do with a language with big integers. Unless you're willing to add Python to the language list...

Answer 11

Java, 198 chars

Saw you mention Java, thought I'd give it a try. This is the best I can get using the standard runtime:

import java.io.*;enum F{F;System s;{try{s.setOut(new PrintStream("a.out"));s.out.print((int)Math.pow(1/(9/Math.pow(10,new java.util.Scanner(new File("a.in")).nextInt())),2));}catch(Exception e){}}}

Answer 12

bash: 69 chars:

w=$(for i in $(seq 1 `<a.in`)
do
echo -n 1
done)
echo $((w**2))>a.out

a.out - really? :)

The only problem: invalid language.

Answer 13

K, 13

Another invalid answer but what the hell.

{a*a:.:x#"1"}

Answer 14

C, 130 chars

char s[1<<27];main(i,n,j){for(read(open("a.in",0),s),n=atoi(s);j=j/10+n-abs(n-i);s[n*2-++i]=48+j%10);fputs(s,fopen("a.out","w"));}