Submission #1368215

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Source Code Expand

#include <iostream>
#include <vector>
#include <map>
using namespace std;

#define rep(i, x) for (int i = 0; i < (x); i++)

int main() {
    int N, X;
    cin >> N >> X;
    vector<int> w(N);
    rep (i, N) {
        cin >> w[i];
    }

    int N1 = (N + 1) / 2,
        N2 = N - N1;
    map<int, int> counter;
    rep (mask, 1 << N1) {
        int sum = 0;
        rep (j, N1) {
            if ((mask >> j) & 1) {
                sum += w[j];
            }
        }
        counter[sum]++;
    }

    int ans = 0;
    rep (mask, 1 << N2) {
        int sum = 0;
        rep (j, N2) {
            if ((mask >> j) & 1) {
                sum += w[N1 + j];
            }
        }
        ans += counter[X - sum];
    }
    cout << ans << endl;

    return 0;
}

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