Submission #392940

#	Time	Username	Problem	Language	Result	Execution time	Memory
392940		cpp219	Tents (JOI18_tents)	C++14	100 / 100	421 ms	71376 KiB

tents

#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define fs first
#define sc second
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 3e3 + 9;
const ll mod = 1e9 + 7;
ll x,y;
ll dp[N][N];

ll f(ll n,ll m){
    if (n*m == 0) return m < y;
    if (dp[n][m] != -1) return dp[n][m];
    ll ans = 0;
    if (m >= 2) ans = (ans + f(n - 1,m - 2)*m*(m - 1)/2)%mod;
    ans = (ans + 4*m*f(n - 1,m - 1) + f(n - 1,m))%mod;
    if (n >= 2) ans = (ans + f(n - 2,m - 1)*m*(n - 1))%mod;
    return dp[n][m] = ans;
}


int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    #define task "tst"
    if (fopen(task".inp","r")){
        freopen(task".inp","r",stdin);
        //freopen(task".out","w",stdout);
    }
    cin>>x>>y; memset(dp,-1,sizeof(dp));
    cout<<f(x,y);
}

Compilation message (stderr)

tents.cpp: In function 'int main()':
tents.cpp:28:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   28 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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