Submission #880751

#	Time	Username	Problem	Language	Result	Execution time	Memory
880751		cpptowin	Tents (JOI18_tents)	C++17	100 / 100	163 ms	197208 KiB

tents

#include<bits/stdc++.h>
#define fo(i,d,c) for(int i=d;i<=c;i++)
#define fod(i,c,d) for(int i=c;i>=d;i--)
#define maxn 1000010
#define N 5010
#define fi first
#define se second
#define pb emplace_back
#define en cout<<"\n";
#define int long long
#define inf 1000000000
#define pii pair<int,int>
#define vii vector<pii>
#define lb(x) x&-x
#define bit(i,j) ((i>>j)&1)
#define offbit(i,j) (i^(1<<j))
#define onbit(i,j) (i|(1<<j))
#define vi vector<int>
template <typename T1, typename T2> bool minimize(T1 &a, T2 b){if (a > b) {a = b; return true;} return false;}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b){if (a < b) {a = b; return true;} return false;}
using namespace std;
const int mod = 1e9 + 7;
int dp[N][N];
int DP(int n,int m,bool ok)
{
    if(dp[n][m] != -1) return dp[n][m];
    int &now = dp[n][m];
    if(n < 1 or m < 1) {
        now = ok;
        return now;
    }
    now = 0;
    now = (now + DP(n - 1,m,ok)) % mod;
    now = (now + 4 * m * DP(n - 1,m - 1,1)) % mod;
    now = (now + m * (m - 1) / 2 * DP(n - 1,m - 2,1)) % mod;
    now = (now + m * (n - 1) * DP(n - 2,m - 1,1)) % mod;
    return now;
}
// From (N, M) we can:
// 1) do nothing and go to (N-1, M)
// 2) put random tent in N-th row in any direction 4*M * (N-1, M-1)
// 3) put 2 tents in N-th row in M*(M-1)/2 * (N-1, M-2)
// 4) put 2 tents in same column s.t. on is in N-th row in M*(N-1)*(N-2, M-1) ways
int n,m;
main()
{
    #define name "TASK"
    if(fopen(name".inp","r"))
    {
       freopen(name".inp","r",stdin);
       freopen(name".out","w",stdout);
    }
    ios_base::sync_with_stdio(false);cin.tie(NULL);
    cin >> n >> m;
    memset(dp,-1,sizeof dp);
    // dp[0][0] = 1;
    cout << DP(n,m,0);
}

Compilation message (stderr)

tents.cpp:45:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   45 | main()
      | ^~~~
tents.cpp: In function 'int main()':
tents.cpp:50:15: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |        freopen(name".inp","r",stdin);
      |        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
tents.cpp:51:15: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |        freopen(name".out","w",stdout);
      |        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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