All max elements and their postition of array

Question

So, for example, I have array: [1, 4, 9, 3, 9]

I need to find all max elements [9, 9] and their index [2, 4]

How can I do this? In C language

int i, pom, max;
max=*gradovi;
for(i=0;i<n;i++) {
  if(*(gradovi+i)>max) {
    max=*(gradovi+i);
    pom=i;
  }
  if(*(gradovi+i)==max) {
    pom=i;
  }
}
return pom;

I need postions of all max elemenents, but this print just last

Answer 1

In any case you need a container that will store the indices of the elements with the maximum value.

You can allocate memory dynamically for such a container.

Here is a demonstrative program.

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

size_t max_elements( const int a[], size_t n, size_t **result )
{
    *result = NULL;
    size_t count = 0;

    if ( n != 0 )
    {
        size_t max_i = 0;
        count = 1;

        for ( size_t i = 1; i < n; i++ )
        {
            if ( a[max_i] < a[i] )
            {
                max_i = i;
                count = 1;
            }
            else if ( !( a[i] < a[max_i] ) )
            {
                ++count;
            }
        }

        *result = malloc( count * sizeof( size_t ) );

        if ( *result != NULL )
        {
            for ( size_t i = max_i, j = 0; i < n && j < count; i++ )
            {
                if ( !( a[i] < a[max_i ] ) ) ( *result )[j++] = i;
            }               
        }           
    }

    return count;
}

int main(void) 
{
    int a[] = { 1, 4, 9, 3, 9 };
    const size_t N = sizeof( a ) / sizeof( *a );

    size_t *result = NULL;

    size_t count = max_elements( a, N, &result );

    for ( size_t i = 0; i < count; i++ )
    {
        printf( "%zu: %d, ", result[i], a[result[i]] );
    }

    putchar( '\n' );

    free( result );

    return 0;
}

Its output is

2: 9, 4: 9,

If the returned value from the function is not equal to 0 but the pointer result was set to NULL then it means that there was a memory allocation error. You can check such a situation.