#include "stdafx.h"
#include <iostream>
#include <conio.h>

using namespace std;

int main()
{
    int *mas=new int[25];
    int N;
    cout << "Input N" << endl;
    cin >> N;
    int *p = new int[N];
    cout << "Input array" << endl;
    for (int i = 0; i < N; i++)
    {
        cin >> p[i];
        cout << i << " Element of array = " << p[i] << endl;

    }
    for (int i = 0; i < N; i++)
    {
        if (p[i] == p[i + 1]||p[i]==p[i+i])
        {
            mas[i] = p[i];
        }
    }
    for (int i = 0; i < N; i++)
    {
        cout << mas[i];
    }

    _getch();
    return 0;
}

#include <iostream>
#include <cstdlib>
#include <ctime>

int main()
{
    const size_t N = 10;
    int a[N];

    std::srand( ( unsigned int )std::time( nullptr ) );

    for ( auto &x : a  ) x = std::rand() % N;

    for ( auto x : a ) std::cout << x << ' ';
    std::cout << std::endl;

    for ( size_t i = 0; i < N; i++ )
    {
        size_t j = 0;
        while ( j != i && a[j] != a[i] ) j++;

        if ( j++ == i )
        {
            while ( j < N && a[j] != a[i] ) j++;

            if ( j != N ) std::cout << a[i] << ' ';
        }
    }
    std::cout << std::endl;

    return 0;
}

1 2 9 5 0 5 2 4 1 8
1 2 5

std::sort( a, a + N );

#include <algorithm>

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <algorithm>

int main()
{
    const size_t N = 10;
    int a[N];

    std::srand( ( unsigned int )std::time( nullptr ) );

    for ( auto &x : a  ) x = std::rand() % N;

    for ( auto x : a ) std::cout << x << ' ';
    std::cout << std::endl;

    std::sort( a, a + N );

    for ( size_t i = 0; i < N; )
    {
        size_t j = i + 1;

        while ( j < N && a[i] == a[j] ) j++;

        if ( j - i > 1 )
        {
            std::cout << a[i] << ' ';
        }

        i = j;
    }
    std::cout << std::endl;

    return 0;
}

for (int i = 0; i < N; i++)
{
    if (p[i] == p[i + 1]||p[i]==p[i+i])
    {
        mas[i] = p[i];
    }
}

if (p[i] == p[i + 1]||p[i]==p[i+i])