B_10816

Sol.1, unordered_map

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void)
{
	int N, M, card;
	unordered_map<int, int> m;
	ios::sync_with_stdio(false);
	cin.tie(0);

	cin >> N;
	for (int i = 0; i < N; i++)
	{
		cin >> card;
		m[card]++;
	}
	cin >> M;
	for (int i = 0; i < M; i++)
	{
		cin >> card;
		cout << m[card] << " ";
	}

}

Sol.2, Binary Search(Upperbound LowerBound)

#include <iostream>
#include <algorithm>

using namespace std;

int arr[500002];
int N, M, card;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> card;
		arr[i] = card;
	}
	sort(arr, arr + N);

	cin >> M;
	for (int i = 0; i < M; i++) {
		cin >> card;
		cout << upper_bound(arr, arr + N, card) - lower_bound(arr, arr + N, card)<<" ";
	}
}