ABC_44 - C - 高橋君とカード / Tak and Cards

#include <bits/stdc++.h>

#define SYNC ios::sync_with_stdio(0);
#define F first
#define S second
#define endl '\n'


using namespace std;

using ll = long long int;
using ii = pair<int, int>;
using vii = vector<ii>;
using vi = vector<int>;
using graph = vector<vi>;
const int INF = 0x3f3f3f3f;
const int MAXN = 58;
const ll mod = 1000000007;

vi x;
int des[MAXN], n, a;
ll dp[58][5500];
int seen[58][5050];
int offset = 2500;
ll sol (int sum, int idx) {
    if (idx == n+1) return !sum;
    if (seen[idx][sum+offset]) return dp[idx][sum+offset];
    seen[idx][sum+offset] = 1;
    return dp[idx][sum+offset] = sol(sum+des[idx], idx+1) + sol(sum, idx+1);
    //cout << dp[idx][sum + offset] << endl;
}

int main() {
    SYNC
    cin >> n >> a;
    x.assign(n+1, 0);
    for (int i = 1; i <= n; ++i) {
        cin >> x[i];
    }
    for (int i = 1; i <= n; ++i) {
        des[i] = x[i] - a;
    }
    cout << sol(0, 1) - 1 << endl;

    return 0;
}