Thread: decimal to number if digits in different bases

anyone knows how they would start this off?

I need a which will take a decimal positive integer x then the program prints the number of digits required to represent the decimal integer x in bases 2, 4, 8, and 16.

For example: If the input is 18, then the output should be:

Given decimal number: 18
Number of digits required in base 2: 5
Number of digits required in base 4: 3
Number of digits required in base 8: 2
Number of digits required in base 16: 2

any help will be appreciated

You could use tables, or a division loop (this is the "bad at math" approach).

You could use exponents/logarithms (this is the "good at math" approach).

how exactly would it start though?

Code:

#include <stdio.h>
#include <math.h>

int main()
{
        int x, a, b, c, d;

        printf("Please enter a number>");
        scanf("%d", &x);

        a=1+(log(x)/log(2));
        b=1+(log(x)/log(4));
        c=1+(log(x)/log(8));
        d=1+(log(x)/log(16));

        printf("Given decimal number: %d\n", x);
        printf("Number of digits required in base 2: %d\n", a);
        printf("Number of digits required in base 4: %d\n", b);
        printf("Number of digits required in base 8: %d\n", c);
        printf(" Number of digits required in base 16: %d", d);

}

it just doesnt compile. it gives me this when i try to compile it. i am using unix

> gcc num-digits.c
Undefined first referenced
symbol in file
log /var/tmp//ccNuKjnz.o
ld: fatal: Symbol referencing errors. No output written to a.out
collect2: ld returned 1 exit status

I would start with a piece of paper and work out a psuedocode algorithm. Since the problem is using the traditional CS bases (2, 4, 8, 16) I would probably draw upon my knowledge of binary.

alright thanks. i got how to do it

I guess the question at hand is what is wrong with needing to compile in the math library? Mingw just does it implicitly. If you were to erase libm.a from your machine you would not be able to compile it with mingw either. Furthermore, you can explictly -lm on mingw and still compile just fine on windows (if your question is something to the effect of "how do I make a single makefile").

I just want the OP to be clear on one thing. For the sake of your makefiles or whatever the -lm is simply ignored by mingw.