Submission #987223

#	Time	Username	Problem	Language	Result	Execution time	Memory
987223		steveonalex	Tents (JOI18_tents)	C++17	100 / 100	131 ms	38804 KiB

tents

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

#define ALL(v) (v).begin(), (v).end()
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)

// mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng(1);
ll rngesus(ll l, ll r){return ((ull) rng()) % (r - l + 1) + l;}

ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}

ll LASTBIT(ll mask){return mask & (-mask);}
ll pop_cnt(ll mask){return __builtin_popcountll(mask);}
ll ctz(ll mask){return __builtin_ctzll(mask);}
ll clz(ll mask){return __builtin_clzll(mask);}
ll logOf(ll mask){return 63 - clz(mask);}

template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b){a = b; return true;}
        return false;
    }
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b){a = b; return true;}
        return false;
    }
template <class T>
    void printArr(T a, string separator = " ", string finish = "\n", ostream& out = cout){
        for(auto i: a) out << i << separator;
        out << finish;
    }
template <class T>
    void remove_dup(T &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }

const int MOD = 1e9 + 7;
const int N = 4000;
int dp[N][N];

void add(int &a, ll b){
    b %= MOD;
    a += b;
    if (a >= MOD) a -= MOD;
}

int main(void){
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int n, m; cin >> n >> m;
    dp[n][m]= 1;

    for(int i = n; i>=0; --i) for(int j = m; j>=0; --j) if (dp[i][j]){
        if (i >= 1) add(dp[i-1][j], dp[i][j]);
        if (i >= 1 && j >= 1) add(dp[i-1][j-1], 1LL * dp[i][j] * 4 * j);
        if (i >= 2 && j >= 1){
            add(dp[i-2][j-1], 1LL * dp[i][j] * (i-1) * j);
        }
        if (j >= 2 && i >= 1){
            add(dp[i-1][j-2], 1LL * dp[i][j] * j * (j-1) / 2);
        }
    }
    

    int ans = 0;
    for(int j = 0; j < m; ++j) add(ans, dp[0][j]);
    cout << ans << "\n";


    return 0;
}

• Subtask 1: 48 / 48
• Subtask 2: 52 / 52