Submission #1274642

#	Time	Username	Problem	Language	Result	Execution time	Memory
1274642		lamlamlam	Tents (JOI18_tents)	C++20	0 / 100	16 ms	35656 KiB

tents

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define endl '\n'
#define task "JOI18_tents"
const int MN = 3005, mod = 1e9+7;
int n,m,dp[MN][MN];
inline int add(int x,int y) {return x+y<mod ? x+y : x+y-mod;}
inline int sub(int x,int y) {return x+y>=0 ? x-y : x-y+mod;}
inline int mul(ll x,ll y) {return x*y<mod ? x*y : (x*y)%mod;}
inline int c2n(int x) {return x*(x-1)/2;}
int f(int i,int j){
    if(dp[i][j]!=-1) return dp[i][j];
    dp[i][j] = add(mul(4*j,dp[i-1][j-1]),dp[i-1][j]);
    if(j>1) dp[i][j] = add(dp[i][j],mul(c2n(j),dp[i-1][j-2]));
    if(i>1) dp[i][j] = add(dp[i][j],mul(j*(i-1),dp[i-2][j-1]));
    return dp[i][j];
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    for(int i=0; i<MN; i++) for(int j=0; j<=MN; j++) dp[i][j] = -1;
    for(int i=0; i<MN; i++) dp[i][0] = dp[0][i] = 1;
    cin >> n >> m;
    cout << sub(f(n,m),1);
    cerr << "\nThoi gian loj: " << clock() << endl;
}

Compilation message (stderr)

tents.cpp: In function 'int main()':
tents.cpp:25:63: warning: iteration 3005 invokes undefined behavior [-Waggressive-loop-optimizations]
   25 |     for(int i=0; i<MN; i++) for(int j=0; j<=MN; j++) dp[i][j] = -1;
      |                                                      ~~~~~~~~~^~~~
tents.cpp:25:43: note: within this loop
   25 |     for(int i=0; i<MN; i++) for(int j=0; j<=MN; j++) dp[i][j] = -1;
      |                                          ~^~~~

• Subtask 1: 0 / 48
• Subtask 2: 0 / 52