Need Help with Smallest and Biggest number from array

Hello,
I need help with my code.
I need to get an average smallest and biggest number from the 20 randomly generated numbers, I have the average but cant get the smallest number and biggest to work.
Btw the random generated numbers have to be up to 8 numbers in a line.

here is my code

Code:

---

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



int main( )
{
int randValues[20] = {0}, sum = 0, i = 0;


srand(time(NULL));


for (i = 0; i < 8; sum += randValues[i], i++)
printf("%d ", randValues[i] = ((rand() % 100)+1));
printf("\n");
for (i = 0; i < 8; sum += randValues[i], i++)
printf("%d ", randValues[i] = ((rand() % 100)+1));
printf("\n");
for (i = 0; i < 4; sum += randValues[i], i++)
printf("%d ", randValues[i] = ((rand() % 100)+1));
printf("\n");


sum /= 20;

printf("\nAverage : %d", sum);

return 0;
}

---

thanks

First off, make sure your code has proper indentation:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
int main( )
{
    int randValues[20] = {0}, sum = 0, i = 0;

    srand(time(NULL));

    for (i = 0; i < 8; sum += randValues[i], i++)
        printf("%d ", randValues[i] = ((rand() % 100)+1));
    printf("\n");

    for (i = 0; i < 8; sum += randValues[i], i++)
        printf("%d ", randValues[i] = ((rand() % 100)+1));
    printf("\n");

    for (i = 0; i < 4; sum += randValues[i], i++)
        printf("%d ", randValues[i] = ((rand() % 100)+1));
    printf("\n");
 
    sum /= 20;
 
    printf("\nAverage : %d", sum);
 
    return 0;
}

---

Why are you using three separate loops to generate your 20 random numbers? Not only does this not make sense, you're also not assigning each random number to a unique position in the array. The second loop overwrites the first 8 elements in the array, and the third loop overwrite the first 4 elements. This means the last 12 elements do not contain any valid values. If you need to print up to 8 numbers per line, just figure out the logic to print a newline when "i" is at specific values.

I'd also suggest putting the sum additions into the body of the loop, rather than in the increment portion of the "for()", for clarity. You might also want to move the assignments to "randValues[i]" out of the "printf()", for the same reason.

Finally, "sum" is in integer, so the resulting "average" will be an integer (any decimal portion will be truncated).

I would suggest putting the min/max aside until you get the unnecessary multiple-loop scenario straightened out. Also, when you're ready, you should show your attempt at finding the min/max.

20 random INTs that I assume can be really high numbers, will overflow sum as that one is also a INT

Why are you doing 8+8+4 loops?, as is you never go over [7] in array, so why even bather having 20 array size
if you want to print a new line after each 8, make the loop 20 but charge to this: if ((i & 7) == 7) printf("\n");

Quote:

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Originally Posted by tonyp12

20 random INTs that I assume can be really high numbers, will overflow sum as that one is also a INT

---

The expression (rand() % 100)+1 means that the numbers actually assigned will be in the range [1, 100], so at most the sum will be 20 * 100 = 2000, which is well within the minimum range guaranteed for int.

Code:

---

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


int main(void)


{
    int sum, average, small, big, x=0;
    int num[20]={0};
    srand(time(NULL));
   
    sum=small=big=num[20]=rand()%100+1;
    printf("%d ",num[x]);
   
    for(x=1;x<20;x++)
    {
        num[x]=rand()%100+1;
        if(num[x]>big)
        {
            big=num[x];
        }
        else if(num[x]<small)
        {
            small=num[x];
        }
        if(x%8==0)
        {
            printf("\n");
        }
        sum+=num[x];
        printf("%d ",num[x]);
    }
    average=sum/20;
    printf("\nBig: %d ",big);
    printf("\nSmall: %d ",small);
    printf("\nAverage: %d ",average);
   
    return 0;
   
}

---

I've done it changed some names too but there is one small problem now. Every time I run the program the first number is 0 but I want it to be random.

Quote:

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Originally Posted by Wlod

I've done it changed some names too but there is one small problem now. Every time I run the program the first number is 0 but I want it to be random.

---

This looks problematic:

Code:

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sum=small=big=num[20]=rand()%100+1;

---

num is an array of 20 elements, hence num[20] does not exist. You should have written:

Code:

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sum = small = big = num[0] = rand() % 100 + 1;

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By the way, this could give you unexpected results:

Code:

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average=sum/20;

---

The reason is that there is integer division. You might want to declare average as a double instead, then write:

Code:

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average = sum / 20.0;

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Of course, you must then also change the printf that prints the average.

Here is a corrected version:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
 
int main(void)
 
 
{
    int small, big;
    float num[21];
    float average;
    float sum;
    srand(time(NULL));


 
 
    /* here is the loading part*/
    int i;
    for(i=1;i<=20;i++){
    num[i]=rand()%100+1;
    //printf("%f\n",num[i]);
    }


    /* initializing */
    sum=0;
    small=num[1];
    big=num[1];


    /* running the cycle */
    for(i=1;i<=20;i++)
    {
        if(num[i]>big)
        {
            big=num[i];
        }
        if(num[i]<small)
        {
            small=num[i];
        }


        sum=sum+num[i];
    }

    /* computing and displaying results */
    average=sum/20.0;
    printf("\nBiggest: %d ",big);
    printf("\nSmallest: %d ",small);
    printf("\nAverage: %f ",average);
   
    return 0;
   
}

---

The main mistakes in your code is that variable average has to be a float, as laserlight pointed out already.

Quote:

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sum=small=big=num[20]=rand()%100+1;

---

This doesn't sound good. If you want to find a minimum of an array, the way to do it is to:

Code:

---

    /* initializing */
    sum=0;
    small=num[1];
    big=num[1];

---

Assign to two variables the first value of the array. And then run a cycle where you compare the first (if you need the sum also) and all the following elements of the array, whether they are smaller than the already found minimum and / or bigger than the already found maximum.

@ nerio: Why are you using an array of size 21 and starting your loops at 1? If the program requires 20 elements, you should just make the array with a size of 20 and start looping at 0.

@ Matticus: because I am used from Pascal that many things just starts from 1. So in C I have these old habits, since C is my first imperative language that I have learned after Pascal.

Code:

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myCoolArray : Array[1..20] of Integer;

---

Quote:

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Originally Posted by nerio

@ Matticus: because I am used from Pascal that many things just starts from 1. So in C I have these old habit, since C is my first imperative language that I have learned after Pascal.

---

But on another thread, you said:

Quote:

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Originally Posted by nerio

Another issue, an array in C starts with 0. So the for cycle should go from...

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So you are clearly aware of this fact.

I would suggest you stick to common C idioms on the C board so as not to confuse new programmers.

ok, here is the corrected code:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
 
int main(void)
 
 
{
    int small, big;
    float num[20];
    float average;
    float sum;
    srand(time(NULL));
 
 
 
 
    /* here is the loading part*/
    int i;
    for(i=0;i<20;i++){
    num[i]=rand()%100+1;
    //printf("%f\n",num[i]);
    }
 
 
    /* initializing */
    sum=0;
    small=num[0];
    big=num[0];
 
 
    /* running the cycle */
    for(i=0;i<20;i++)
    {
        if(num[i]>big)
        {
            big=num[i];
        }
        if(num[i]<small)
        {
            small=num[i];
        }
 
 
        sum=sum+num[i];
    }
 
    /* computing and displaying results */
    average=sum/20.0;
    printf("\nBiggest: %d ",big);
    printf("\nSmallest: %d ",small);
    printf("\nAverage: %f ",average);
     
    return 0;
     
}

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Quote:

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Originally Posted by Matticus

common C idioms

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I guess that there is something new I learn every day:

https://en.wikipedia.org/wiki/Programming_idiom
http://cboard.cprogramming.com/c-pro...ed-idioms.html
arrays - C Idioms and little known facts - Stack Overflow
Idioms for C programmers (COMP 40)

Thank you Matticus.

Quote:

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Originally Posted by nerio

I guess that there is something new I learn every day:

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That's why I enjoy spending my time here.

Nice finds, by the way. Thanks for sharing the links.

Quote:

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Originally Posted by nerio

Thank you Matticus.

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My pleasure!

Thanks Everyone It works now :D