Найти количество общих элементов в массивах.

#include "stdafx.h"
#include "iostream"
 
using namespace std;
 
int i = 0, j = 0, n =  0;
 
int array[6] = {1, 2, 3, 4, 5, 6};
int array1[6] = {3, 4, 5, 6, 7, 8};
 
int main()
{
    for(i = 0; i != 6; i++)
    {
        for(j = 0; j != 6; j++)
        {   
            if(array[i] == array1[j])
                n++;
        }
    }
    cout<<n<<endl;
    system("pause");
    return 0;
}

while(i < 6 && j < 6)
...

#include <iostream>
#include <set>
#include <vector>
#include <algorithm>
 
void massiv() {
    std::cout << "massiv() :\n";
 
    static const size_t MASSIV_SIZE = 6;
 
    int a[MASSIV_SIZE] = {3,1,6,4,5,2};
    int b[MASSIV_SIZE] = {8,4,5,9,7,6};
    std::sort(a, a + MASSIV_SIZE);
    std::sort(b, b + MASSIV_SIZE);
 
    std::copy(a, a + MASSIV_SIZE, std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
 
    std::copy(b, b + MASSIV_SIZE, std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
 
    std::vector<int> intersection;
    std::set_intersection(a, a + MASSIV_SIZE, b, b + MASSIV_SIZE, back_inserter(intersection));
 
    std::copy(intersection.begin(), intersection.end(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
}
 
void set() {
    std::cout << "set() :\n";
 
    std::set<int> set1;
    set1.insert(3);
    set1.insert(1);
    set1.insert(6);
    set1.insert(4);
    set1.insert(5);
    set1.insert(2);
 
    std::set<int> set2;
    set2.insert(8);
    set2.insert(4);
    set2.insert(5);
    set2.insert(9);
    set2.insert(7);
    set2.insert(6);
 
    std::copy(set1.begin(), set1.end(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
 
    std::copy(set2.begin(), set2.end(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
 
    std::vector<int> intersection;
    std::set_intersection(set1.begin(), set1.end(), set2.begin(), set2.end(), back_inserter(intersection));
 
    std::copy(intersection.begin(), intersection.end(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
}
 
int main() {
    massiv();
    set();
 
    return 0;
}

#include<iostream>
const int NA = 5;
const int NB = 7;
 
int Count(int *a, int *b, int na, int nb)
{
    int i = 0, j = 0, count = 0;
    while(i < na && j < nb)
    {
        while(a[i] < b[j])
            ++i;
        while(b[j] < a[i])
            ++j;
        if (i < na && j < nb  && a[i] == b[j])
        {
            ++i, ++j, ++count;
        }
    }
    return count;
}
 
int main()
{
   int a[NA] = {1, 2, 5, 7, 10}, b[NC] = {0, 1, 2, 3, 7, 10 ,11};
   std::cout << Count(a, b, NA, NB);
   return 0;
}

#include<iostream>
const int NA = 5;
const int NB = 7;
 
int Count(int *a, int *b, int na, int nb)
{
    int i = 0, j = 0, count = 0;
    while(i < na && j < nb)
    {
        if(a[i] < b[j])
            ++i;
        else if(b[j] < a[i])
            ++j;
        else
        {
            ++i, ++j, ++count;
        }
    }
    return count;
}
 
int main()
{
   int a[NA] = {1, 2, 3, 7, 10}, b[NC] = {0, 1, 2, 3, 7, 10 ,11};
   std::cout << Count(a, b, NA, NB);
   return 0;
}