alternative for STL - test/main

test_main.cpp

#include <cstdio>
// if you want to use STL, uncomment following includes:
// #include <vector>
// #include <algorithm>
// using namespace std;

// count "key" from array sized n
// if no key, print "NO"
int main() {
    int n;
    scanf("%d", &n);
    vector<int> v(n);
    for (int i = 0; i < v.size(); ++i) scanf("%d", &v[i]);
    sort(v.begin(), v.end());
    for (int i = 0; i < v.size(); ++i) printf("%d ", v[i]); puts("");

    int key;
    scanf("%d", &key);

    if (binary_search(v.begin(), v.end(), key)) {
        int equal_count = upper_bound(v.begin(), v.end(), key) - lower_bound(v.begin(), v.end(), key);
        printf("%d\n", equal_count);
    }
    else {
        puts("NO");
    }
    return 0;
}