>when I try to use functions to make a program, i do not know how to use arrays
On the surface, nothing changes. You declare an array as a function parameter the same way. The only difference is that you don't need the size, and it's a good idea to pass the size as a separate parameter:
#include <iostream>
void print_array ( int a[], int size )
{
for ( int i = 0; i < size; i++ )
std::cout<< a[i] <<'\n';
}
int main()
{
int a[] = {1,2,3,4,5};
print_array ( a, 5 );
}
>I am lost on how to find that duplicate!
Rash's suggestion is the simplest (and you should use it for now), but far from the most efficient. Just as a taste of the other options, you can sort the array and then check adjacent values to see if they're the same, or you can use an existence table:
#include <iostream>
template <typename T, int sz>
char (&array(T(&)[sz]))[sz];
void print_duplicates ( int a[], int size )
{
int exist[10] = {0};
for ( int i = 0; i < size; i++ )
++exist[a[i]];
for ( int i = 0; i < sizeof array ( exist ); i++ ) {
if ( exist[i] > 1 )
std::cout<< i <<" is duplicated "
<< exist[i] - 1 <<" times\n";
}
}
int main()
{
int a[] = {5,4,7,6,5,6,7,8,9,3,4,5,6,7,8};
print_duplicates ( a, sizeof array ( a ) );
}
An existence table is an array of counters, where the value in the original array is the index. By using a[0] as the index for exist, exist[5] is incremented. This is not an good method when the possible ranges are big because you need an array that can hold every possible value, but other methods (such as using a std::map can be generalized quite nicely, though you lose the linear performance.
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