Submission #362325

#	Time	Username	Problem	Language	Result	Execution time	Memory
362325		knightron0	Tents (JOI18_tents)	C++14	100 / 100	448 ms	71404 KiB

tents

#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define fr first
#define sc second
#define clr(a, x) memset(a, x, sizeof(a))
#define dbg(x) cout<<"("<<#x<<"): "<<x<<endl;
#define printvector(arr) for (auto it = arr.begin(); it != arr.end(); ++it) cout<<*it<<" "; cout<<endl;
#define all(v) v.begin(), v.end()
#define lcm(a, b) (a * b)/__gcd(a, b)
#define int long long int
#define printvecpairs(vec) for(auto it: vec) cout<<it.fr<<' '<<it.sc<<endl;
#define endl '\n'
#define float long double

const int MOD = 1e9 + 7;
const int INF = 2e15;
const int MAXN = 3005;

int n, m;
int dp[MAXN][MAXN];
int modinv = 0;

int fastexpo(int b, int exp){
    if(exp == 0) return 1;
    if(exp == 1) return b;
    int ans = (fastexpo(b,exp/2) % MOD);
    ans *= ans;
    ans %= MOD;
    if(exp % 2 == 1){
        ans *= b;
    }
    ans %= MOD;
    return ans;
}

int nc2(int n){
	int ans = n%MOD;
	ans *= (n-1+MOD)%MOD;
	ans %= MOD;
	return ans*modinv;
}

int f(int lx, int ly){
	if(lx < 0 || ly < 0) return 0;
	if(lx == 0 || ly == 0) return 1;
	if(dp[lx][ly] != -1) return dp[lx][ly];
	return dp[lx][ly]= (((4*((lx%MOD)*(f(lx-1, ly-1)%MOD))%MOD)%MOD) + ((((ly-1)%MOD)*(lx%MOD)*(f(lx-1, ly-2)%MOD)%MOD)%MOD) + ((nc2(lx)%MOD)*(f(lx-2,ly-1)%MOD)%MOD) + ((f(lx, ly-1)%MOD)%MOD))%MOD;
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    #ifdef LOCAL
    freopen("input.txt", "r", stdin);
    #endif
    cin>>n>>m;
    clr(dp, -1);
    modinv = fastexpo(2, MOD-2);
    cout<<(f(n, m)+MOD-1)%MOD<<endl;
    return 0;
}

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