Integer programming question in C

wongfoo · 06-17-2006, 08:36 AM

im trying to do a small program in C for the following question and would approeciate any help:

To round of an integer i to the next largest even multiple of another integer j, the following formula can be used:

Next_multiple = i + j - i % j

Write a program to find the next largest even multiple for the following values of i and j:

i:: j

365:: 7
12,258:: 23
996:: 4

(i and the corresponding j value)

this is the program code that I attempted

Code:

#include <stdio.h>

int main (void)
{
    int i;
    int j;
    int nextmultiple;

    nextmultiple = (i + j) - (i % j);

    i = 365;
    j = 7;

    printf ("The next largest even multiple when i = 365 and j = 7 is %i\n", nextmultiple);

    i = 12258;
    j = 23;

    printf ("The next largest even multiple when i = 12,258 and j = 23 %i\n", nextmultiple);

    i = 996;
    j = 4;

    printf ("The next largest even multiple when i = 996 and j = 4 %i\n", nextmultiple);

    return 0;
}

ps. this was compiled in Windows

taylor_venable · 06-17-2006, 08:56 AM

Quote:

Originally Posted by wongfoo

Code:

int nextmultiple;
nextmultiple = (i + j) - (i % j);

You probably want nextmultiple to be a function instead of an integer holding some value derived from garbage (uninitialized) integers i and j. The contents of nextmultiple are not going to be re-evaluated whenever the variable is used.

exvor · 06-17-2006, 11:47 AM

Hmmmm yes what taylor said is correct. In C you cannot define a varable this way.

more to do this as a function and run the function every time. If this is homework please investigate further why your program is wrong and not just use this as the answer as you will be more confused later

what you probably want to do is somehting like this

Code:

#include<stdio.h> 
int findvalue(int,int); 

int main()
{ 


    int i = 0; 
    int j = 0; 
  
 

    i = 365; 
    j = 7; 
    printf("The next largest even multiple when i = 365 and j = 7 is %d",findvalue(i,j)); 

/* Do more like this */ 


return 0; 
}

int findvalue(int x, int y)
{ 
    int temp = 0; 
    
    temp = (x + y) - (x % y); 
    return temp; 
}

Also if you havent gone over function calls and variable passing then your instructer may see this as cheating. He probably wants you to do it the long way.

wongfoo · 06-22-2006, 08:15 AM

is there a way to do it without function calls and variable passing?

i appreaciate any help.

Flesym · 06-22-2006, 08:32 AM

Quote:

is there a way to do it without function calls and variable passing?
i appreaciate any help.

Yes and no! -Actually you cannot write a C program without function calls (remember that even the call of 'main' is such one). But I guess this is not what you want know. You can of course re-calculate the value of "nextmultiple" each time you changed 'i' or 'j' (simply copy/paste the assignment of it under every change of 'i' or 'j'). I think this will accomplish what you want. But what you want is really no good style. Unless your teacher forbids the use of extra functions, you should really use them! -Btw. 'printf' is also a function.

wongfoo · 06-22-2006, 08:58 AM

thanks Flesym

wongfoo · 06-23-2006, 09:56 AM

ive written a small program to accept 2 integeres and then divide the first one by the second.

the code is:

Code:

int main (void)
{
    int i, j;
    float result;

    printf ("Please enter two integers.\n");
    scanf ("%i %i", &i, &j);

    if ( j == 0 )
        printf ("\nDivision by zero.\n");
    else
        result = (float) i / j;
        printf ("\nThe result is %f\n", result);

    return 0;
}

the only thing is that when i divide by zero it shows 'Division by zero' as well as the result, when it should only show the division by zero.

any suggestions or help would be appreciated.

could someone also tell me how to compile and run c programs in kubuntu? which program should i use?

thanks

xhi · 06-23-2006, 10:06 AM

without brackets your else will only apply to one line.

Code:

else
{
       result = (float) i / j;
       printf ("\nThe result is %f\n", result);
}

Flesym · 06-23-2006, 10:14 AM

And the answer to your other question

Quote:

Originally Posted by wongfoo

could someone also tell me how to compile and run c programs in kubuntu? which program should i use?

Like on any other Linux system you can use gcc for compilation. If it isn't installed already, do this with:

Code:

sudo apt-get install gcc

wongfoo · 06-23-2006, 10:22 AM

thanks for your help xhi and Flesym

how would I compile and output the file from the command line?

xhi · 06-23-2006, 10:27 AM

heh. i didnt read the whole way through the first time.

try `man gcc` to see all the options.

it can be as simple as

gcc filename.c

and your output will be named a.out.. (or you can name the output with the -o option)

then run it from the current dir with ./a.out

taylor_venable · 06-23-2006, 11:24 AM

If you're new to C programming, I recommend taking a look at some of the good tutorials scattered about the internet. Just do an internet search for "c programming tutorial"; here's one I found: http://vergil.chemistry.gatech.edu/r...orial/toc.html

wongfoo · 06-24-2006, 10:55 AM

thanks for your help people.

taylor i'm already working from internet tutorials and questions.

and ive got another one, this one for a simple calculator thats supposed to work like a pocket calculator, ie. enter the number followed by the sign and then enter.

its supposed to start when the user enters the number followed by the 'S' character and then exit the program and print the results when the user enters 0 E. what its doing is looping on entering the first character when it shouldnt.

Code:

#include <stdio.h>

int main (void)
{
    float number, result;
    char sign;


    printf ("Begin Calculations\n");
    scanf ("%f %c", &number, &sign);

    result = 0;

    if ( sign != 'e' ) {
    switch ( sign )
    {
        case 'S':
            result = number;
            printf ("\n%f", result);
            break;
        case '+':
            result = result + number;
            printf ("\n%f", result);
            break;
        case '-':
            result = result - number;
            printf ("\n%f", result);
            break;
        case '/':
            if ( i == 0 )
                printf ("\nDivision by zero.");
            else
                {
                result = result / number;
                printf ("\n%f", result);
                }
            break;
        case '*':
            result = result * number;
            printf ("\n%f", result);
            break;
        default:
            printf ("Unknown operator.\n");
            break;
    }
    }

    printf ("\nThe result of the calculations are %f", result);
    printf ("\nEnd of calculations.\n");

    return 0;

}

id appreciate any help from experienced programmers.

thanks.

also how do you do a 'clear screen' in C ?

xhi · 06-24-2006, 01:09 PM

i dont understand what you are saying the problem is.

>what its doing is looping on entering the first character when it shouldnt.
i dont see a loop here

dinojerm · 06-24-2006, 01:54 PM

You probably want to enclose most of that code in a loop, perhaps something like this:

Code:

do {
scanf ("%f %c", &number, &sign);
//Calculation code
} 
while(sign!='e');
printf ("\nThe result of the calculations are %f", result);