백준 1940번: 주몽

https://www.acmicpc.net/problem/1940

1940번: 주몽

#include <iostream>
#include <sstream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <list>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <stack>
#include <math.h>
#include <memory.h>
using namespace std;

#define MAX_SIZE 100
#define INF 0x7fffffff
#define CENDL "\n"
#define ll long long

#define c_reverse(s) reverse(s.begin(), s.end())
#define c_sort(s) sort(s.begin(), s.end())
#define print_vector(v) for(int i=0; i<v.size(); i++) cout << v[i];

int main() {

    cin.tie(0);
    std::ios::sync_with_stdio(false);

    long long n, k; cin >> n >> k;

    int sol = 0;
    set<int>st;
    
    for (int i = 0; i < n; i++) {
        int d;
        cin >> d;
        if (k >= d && st.count(k - d) == 0) {
            st.insert(d);
        }
        else if (k >= d) {
            sol++;
        }
    }
    
    cout << sol << CENDL;
    return 0;
}