Submission #838454

#	Time	Username	Problem	Language	Result	Execution time	Memory
838454		Charizard2021	Magneti (COCI21_magneti)	C++17	110 / 110	106 ms	14924 KiB

Main

#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
long long fact[100002], inv[100002];

long long pw(long long b, long long e)
{
	long long ans = 1;

	while(e)
	{
		if(e & 1)
			ans = (ans * b) % MOD;
		b = (b * b) % MOD;
		e >>= 1;
	}

	return ans;
}

long long C(long long n, long long k)
{
    if(n < k){
        return 0;
    }
	long long ans = fact[n];
	ans *= inv[k];
	ans %= MOD;
	ans *= inv[n-k];
	ans %= MOD;
	return ans;
}
int main(){
	fact[0] = 1;
	for(long long i = 1; i <= 100000; i++){
		fact[i] = (fact[i-1] * i) % MOD;
    }
	inv[0] = 1;
	for(long long i = 1; i <= 100000; i++){
		inv[i] = pw(fact[i], MOD-2);
	}
    long long n, l;
    cin >> n >> l;
    long long r[1 + n];
    for(long long i = 1; i <= n; i++){
        cin >> r[i];
    }
    sort(r + 1, r + n + 1);
    bool allEqual = true;
    for(long long i = 1; i < n; i++){
        if(r[i] != r[i + 1]){
            allEqual = false;
            break;
        }
    }
    if(allEqual){
	    cout << (fact[n] * C(l - (n - 1) * r[1] - 1 + n, n)) % MOD << "\n";
    }
    else{
        vector<vector<vector<long long> > > dp(2, vector<vector<long long> >(5 + n, vector<long long>(5 + l, 0)));
        dp[0][0][0] = 1;
        long long cur = 0;
        for(long long i = 1; i <= n; i++){
            cur ^= 1;
            dp[cur][0][0] = 0;
            long long rad = r[i];
            for(long long j = 1; j <= i; j++){
                for(long long k = 1; k <= l; k++){
                    dp[cur][j][k] = dp[!cur][j - 1][k - 1];
                    if(k >= rad){
                        dp[cur][j][k] = (dp[cur][j][k] + (dp[!cur][j][k - rad] * 2 * j) % MOD) % MOD;
                    }
                    if(k >= 2 * rad - 1){
                        dp[cur][j][k] = (dp[cur][j][k] + (dp[!cur][j + 1][k - 2 * rad + 1] * j * (j + 1)) % MOD) % MOD;
                    }
                }
            }
        }
        long long ans = 0;
        for(long long i = 1; i <= l; i++){
            ans = (ans + (dp[cur][1][i] * C(l - i + n, n)) % MOD) % MOD;
        }
        cout << ans << "\n";
    }
}

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