백준 s4 1822 차집합 c++

https://www.acmicpc.net/problem/1822

1822번: 차집합

 

/*boj s4 1822 차집합*/
#include <algorithm>
#include <iostream>
#include <vector>
#define MAXN 500010
using namespace std;

int N, M;
int A[MAXN];
int B[MAXN];
vector<int> ans;

int main(void) {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin >> N >> M;
    for (int i = 0; i < N; i++)
        cin >> A[i];
    for (int j = 0; j < M; j++)
        cin >> B[j];

    sort(A, A + N);
    sort(B, B + M);

    for (int i = 0; i < N; i++) {
        if (binary_search(B, B + M, A[i]) == 0) {
            ans.push_back(A[i]);
        }
    }

    if (ans.size() == 0)
        cout << 0 << "\n";
    else {
        cout << ans.size() << "\n";
        for (int a : ans) {
            cout << a << " ";
        }
    }
}