Submission #1059042

#	Time	Username	Problem	Language	Result	Execution time	Memory
1059042		RiverFlow	Magneti (COCI21_magneti)	C++14	110 / 110	20 ms	14552 KiB

Main

#include <bits/stdc++.h>

#define nl "\n"
#define no "NO"
#define yes "YES"
#define fi first
#define se second
#define vec vector
#define task "main"
#define _mp make_pair
#define ii pair<int, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
#define unq(x) sort(all(x)); x.resize(unique(all(x)) - x.begin())

using namespace std;

template<typename U, typename V> bool maxi(U &a, V b) {
    if (a < b) { a = b; return 1; } return 0;
}
template<typename U, typename V> bool mini(U &a, V b) {
    if (a > b) { a = b; return 1; } return 0;
}

const int mod = (int)1e9 + 7;

void prepare(); void main_code();

int main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    const bool MULTITEST = 0; prepare();
    int num_test = 1; if (MULTITEST) cin >> num_test;
    while (num_test--) { main_code(); }
}
const int N = (int)52;
const int L = (int)1e4 + 7;

int Pow(int a, long long b) {
    int res = 1;
    for(; b > 0; b >>= 1, a = 1ll * a * a % mod)
        if (b & 1) res = 1ll * res * a % mod;
    return res;
}

int P[L], F[L];

int add(int a, int b) { return a + b < mod ? a + b : a + b - mod; }
int sub(int a, int b) { return a >= b ? a - b : a - b + mod; }
int mul(int a, int b) { return 1LL * a * b % mod; }
int C(int k, int n) {
    return mul(P[n], mul(F[k], F[n - k]));
}
int distribute(int k, int n) {
    return C(n - 1, n + k - 1);
}
void prepare() {
    const int n = L - 3;
    P[0] = 1;
    FOR(i, 1, n) P[i] = mul(P[i - 1], i);
    F[n] = Pow(P[n], mod - 2);
    FOD(i, n - 1, 0) F[i] = mul(F[i + 1], i + 1);
};

int r[N];

void Add(int &a, int b) {
    a += b;
    if (a >= mod) a -= mod;
}

int dp[N][N][L];

void main_code() {
    int n, l;
    cin >> n >> l;
    FOR(i, 1, n) cin >> r[i];
    sort(r + 1, r + n + 1);

    FOR(i, 0, n - 1) r[i] = r[i + 1];

    dp[1][1][1] = 1;
    for(int i = 1; i < n; ++i)
    for(int j = 1; j <= i; ++j)
    FOR(k, 1, l) if (dp[i][j][k] > 0) {
        // new_set
        Add(dp[i + 1][j + 1][k + 1], mul(j + 1, dp[i][j][k]));
        // extend
        if (k + r[i] <= l)
            Add(dp[i + 1][j][k + r[i]], mul(2 * j, dp[i][j][k]));
        // merge
        if (k + 2 * r[i] - 1 <= l and j > 1)
            Add(dp[i + 1][j - 1][k + 2 * r[i] - 1], mul(j - 1, dp[i][j][k]));
    }
    int ans = 0;
    FOR(d, 1, l) {
        // dp[n][1][d]
        int f = dp[n][1][d];
        f = mul(f, distribute(l - d, n + 1));
        Add(ans, f);
    }
    cout << ans;

}


/*     Let the river flows naturally     */

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:35:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:36:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 30 / 30
• Subtask 4: 50 / 50