Thread: C Programming using Arrays.

Having some issues with this problem.

Given an array of 100 random numbers in the range 1 to 999, write a function for each of the following processes. In building the arrays, if the random number is evenly divided by 3 or 7, store it as a negative number.

(a) Print the array ten values to a line. Make sure that the values are aligned in rows.
(b) Print the odd values, ten to a line.
(c) Print the values at the odd numbered index locations, ten to a line.
(d) Return a count of the number of even values.
(e) Return the sum of all values in the array.
(f) Return the location of the smallest value in the array.
(g) Copy all possible values to a new array. Then use process (a) above to print the new array.
(h) Copy all negative values to a new array. Then use process (a) above to print the new array.

This is what I have so far:

Code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int ranary[100];
    int randnum;
    int randNos[100];
    
    for (int i = 0; i < 100; i++)
        {
             do
                {
                 randnum = rand() %100;
                } while (randnum[ranary] == 1);
             ranary[randnum] = 1;
             randNos[i] = randnum;
             
             if(randNos[i] % 3 == 0 || randNos[i] % 7 == 0);
             	{
           		 randNos[i] *= (-1);
                }              
        }
        

    
    system("pause");
    return 0;
}

Not sure at all how to generate random number 1-999 correctly as It's hard to base it off the book: "Computer Science: A Structured Programming Approach Using C" when your teacher does things slightly different..

Mhm, Once I make the random array I'll be using functions for each part of the problem. The code that you posted, is that all I need for the random array? Is the if statement for the 3 and 7 correct?

Yep, that's all it takes to initialize the array.

For the if() clause ... The assignment says to store it as a negative number, not minus one...

Code:

  for (x = 0; x < 100; x ++)
    if ( (rndarray[x] % 3 == 0) || (rndarray[x] % 7 == 0))   
      rndarray[x] = 0 - rndarray[x];

And yes, I would do it in two separate loops although, strictly speaking, it's not necessary. It makes for easier debugging later.

`time' cannot be used as a function

I put #include <time.h> and identified it but I get that error.

Originally Posted by Justin Ling

`time' cannot be used as a function

I put #include <time.h> and identified it but I get that error.

Code:

#include <time.h>
#include <stdio.h>

int main (void)
  { srand(time(NULL));

    return 0; }

Does that give you the error?

Pleas post your current code for this section...

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main()
{
    int rndarray[100];   // array
    int x;                   // index
    int time;

    srand(time(NULL));  // initialize random sequencer

    for (x = 0; x < 100; x++)
    {
        rndarray[x] = rand() % 1000;
    }
            
    for (x = 0; x < 100; x ++)
    {
        if ( (rndarray[x] % 3 == 0) || (rndarray[x] % 7 == 0))   
        rndarray[x] = 0 - rndarray[x];
    }   

    
    system("pause");
    return 0;
}

Remove the int time declaration... it is overshadowing the time() function in time.h. The compiler only sees the newest declaration of things so when you made time into a variable, you prevented it from seeing time() as a function. Then it should work...

Yup! I'll keep working on it, thanks for the help.

Originally Posted by Justin Ling

Yup! I'll keep working on it, thanks for the help.

Good stuff... get as far along as you can. If you run into trouble... post up your code and we'll see what we can do...

Hmm not sure how to do c. what are the index locations? Gonna skip and do the rest.

This is what I have so far.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void printarray(int rndarray[]);
void oddarray(int rndarray[]);
int countevenary(int rndarray[]);
int sumary(int rndarray[]);


int main()
{
    int rndarray[100];   // array
    int x;                   // index

    srand(time(NULL));  // initialize random sequencer

    for (x = 0; x < 100; x++)
    {
        rndarray[x] = rand() % 1000;
    }
    
    printarray(rndarray);
    oddarray(rndarray);

    system("pause");
    return 0;
}


void printarray(int rndarray[])
{
     int x;
     int numPrinted = 0;    
    for (x = 0; x < 100; x++)
    {
        if ((rndarray[x] % 3 == 0) || (rndarray[x] % 7 == 0))   
        rndarray[x] = 0 - rndarray[x];
    }
    
    printf("The array ten values to a line\n\n");
    
    for (x = 0; x < 100; x++)
    {
        printf("%3d ", rndarray[x]); // prints 10 numbers to a line
        if (numPrinted < 9)
            numPrinted++;
        else
        {
            printf("\n");
            numPrinted = 0;
        }
    }
}

void oddarray(int rndarray[])
{
    int x;
    int numPrinted = 0;
    printf("\n\nThe odd values of the array\n\n");
    
    for (x = 0; x < 100; x++)
    {
        if (rndarray[x] % 2 == 0)
        printf("");
        else
        {
        printf("%3d ", rndarray[x]); // prints 10 numbers to a line
        if (numPrinted < 9)
            numPrinted++;
        else
        {
            printf("\n");
            numPrinted = 0;
        }
        }

    }
    
    printf("\n\n");
}

Originally Posted by Justin Ling

Hmm not sure how to do c. what are the index locations? Gonna skip and do the rest.

Code:

     type   name  indexes                    
       int    array  [100]

Otherwise .... looking a lot better than at first...

bump.

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