[Java] 백준 1208번 부분수열의 합 2 - 투 포인터 / Int, Long 혼용 주의!

https://www.acmicpc.net/problem/1208

1208번: 부분수열의 합 2

부분수열의 합 자체는 Int 범위라는 것에 낚여서

경우의 수가 최대 2^40 이라는 것을 깜빡했다...

그냥 헷갈리면 long때리자

 

 

import java.util.*;
import java.io.*;

public class g1_1208 {
    static FastScanner fs = new FastScanner();
    static PrintWriter pw = new PrintWriter(System.out);
    static int n, s;

    public static void main(String[] args) {
        n = fs.nextInt();
        s = fs.nextInt();
        int[] p1 = fs.readArray(n / 2);
        int[] p2 = fs.readArray(n - n / 2);

        PriorityQueue<Integer> priq1 = new PriorityQueue<>();
        PriorityQueue<Integer> priq2 = new PriorityQueue<>(Collections.reverseOrder());

        fill(priq1, p1, 0, 0);
        fill(priq2, p2, 0, 0);
        
        long cnt = 0, n1 = priq1.poll(), n2 = priq2.poll();
        while (true){
            if (n1 + n2 == s){
                long c1 = 1, c2 = 1;
                while (!priq1.isEmpty() && priq1.peek() == n1){
                    c1++;
                    priq1.poll();
                }
                while (!priq2.isEmpty() && priq2.peek() == n2){
                    c2++;
                    priq2.poll();
                }
                cnt+= c1 * c2;

                if (priq1.isEmpty() || priq2.isEmpty()) break;
                n1 = priq1.poll();
                n2 = priq2.poll();
            }
            else if (n1 + n2 < s){
                if (priq1.isEmpty()) break;
                n1 = priq1.poll();
            }
            else{
                if (priq2.isEmpty()) break;
                n2 = priq2.poll();
            }
        }

        if (s == 0) cnt--;
        pw.println(cnt);
        pw.close();
    }

    static void fill(PriorityQueue<Integer> priq, int[] p, int ptr, int sum){
        if (ptr == p.length){
            priq.add(sum);
            return;
        }
        fill(priq, p, ptr + 1, sum);
        fill(priq, p, ptr + 1, sum + p[ptr]);
    }

    // ----------input function----------

    static void sort(int[] a) {
        ArrayList<Integer> L = new ArrayList<>();
        for (int i : a)
            L.add(i);
        Collections.sort(L);
        for (int i = 0; i < a.length; i++)
            a[i] = L.get(i);
    }

    static class FastScanner {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while (!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] readArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }
}