C++ program cant find mistake [closed] - c++

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this program creates random number array where elements wit arguments 1,3,5,7...,19 are negative and this program should find biggest negative element but when l test program it writes some random number (6784345 instead of array element) can you help me find mistake ?
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
void najneg(int *pa,int *nn)
{
nn=0;
for(int i=0;i<20;i++)
{
if((pa+i)<nn) nn=(pa+i);
}
}
int main()
{
int a[20],nn,i;
srand(time(0));
for(i=0;i<20;i++)
{
if(i%2==0) a[i]=rand()%(61);
else
a[i]=(rand()%(61))*(-1);
}
printf("Formirani niz je:\n");
for(int i=0;i<20;i++)
{
printf("\ "); printf("%d",a[i]);
}
najneg(a,&nn);
printf("\n\nNajveci negativni clan niza je:%d\n",nn);
return 0;
}

Answer 1

In this code, …
void najneg(int *pa,int *nn)
{
nn=0;
for(int i=0;i<20;i++)
{
if((pa+i)<nn) nn=(pa+i);
}
}
you forgot to dereference the pointers,
void najneg(int *pa,int *nn)
{
*nn=0;
for(int i=0;i<20;i++)
{
if(*(pa+i)<*nn) *nn=*(pa+i);
}
}
The most important fix for this function is to change its name to something readable and self-descriptive, with no arbitrary shortenings. When choosing names, think about making the calling code readable and clear. So E.g., najneg → most_negative_value_in.
Secondly, instead of logical out-argument, use the function return value.
Third, if the function doesn't need to change data, use const to let it offer a guarantee that it won't change the data.
Fourth, avoid magic numbers like 20: pass the array size as argument.
This, plus some purely cosmetic changes, yields:
int most_negative_number_in(int const* const a, int const size)
{
int n=0;
for(int i=0; i<size; ++i)
{
if(a[i]<n) { n = a[i] };
}
return n;
}

Answer 2

This function should be
void najneg(int *pa,int *nn)
{
*nn=0; //As you want to modify nn.
for(int i=0;i<20;i++)
{
if(pa[i]<*nn) *nn=pa[i]; //Here, you want to compare values and swap them. Not just address.
}
}
Do not try to complicate it.

Answer 3

In addition to what others have pointed out:
You can simplify the content of your for loops:
for(i = 0; i < 20; i++)
{
// The array slot is assigned a random value
// whether the index is positive or negative.
a[i] = rand() % 61;
// If the index is odd, change the value
// to a negative number.
if(i % 2 == 1)
{
a[i] *= -1;
}
}
In the next loop, you should combine into one printf call:
for(int i = 0; i < 20; i++)
{
printf("\ %d", a[i]);
}
Also, what is "\ " in the format specifier, a tab or a space?