Thread: Need Help with Smallest and Biggest number from array

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.

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.

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:

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:

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

By the way, this could give you unexpected results:

Code:

average=sum/20;

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

Code:

average = sum / 20.0;

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.

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.

@ 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:

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