P7.12 P12675 Common elements

#include <iostream>
#include <vector>
using namespace std;


int common_elements(const vector<int>& X, const vector<int>& Y) {
        int common = 0;
        int x = X.size();
        int y = Y.size();
        int i = 0;
        int j = 0;
        while (i <= x-1 && j <= y-1) {
                if (X[i] == Y[j]) {
                        ++common;
                        ++i;
                        ++j;
                }
                else if (X[i] > Y[j]) {
                        ++j;
                }
                else if (X[i] < Y[j]) {
                        ++i;
                }
        }

        return common;
}

// (c) Carlos Sansón (Best pro1 delegate ever for sure) @csansoon