Submission #489789

#	Time	Username	Problem	Language	Result	Execution time	Memory
489789		CSQ31	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	19 ms	22976 KiB

kangaroo

#pragma GCC optimize("Ofast") 
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define sz(a) a.size()
#define all(a) a.begin(),a.end()
#define lb lower_bound
#define ub upper_bound
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
#define MOD (ll)(1e9+7)
#define INF (ll)(1e18)
#define debug(...) fprintf(stderr, __VA_ARGS__),fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false);\
debug("%s time : %.4fs\n", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))
typedef long long int ll;
typedef long double ld;
typedef pair<ll,ll> PII;
typedef pair<int,int> pii;
typedef vector<vector<int>> vii;
typedef vector<vector<ll>> VII;
ll gcd(ll a,ll b){if(!b)return a;else return gcd(b,a%b);}
ll dp[2001][2001];
int main()
{
	int n,a,b;
	cin>>n>>a>>b;
	dp[1][1] = 1;
	for(int i=2;i<=n;i++){
		for(int j=1;j<=i;j++){
			if(i==a || i==b){
				dp[i][j] = dp[i-1][j-1] + dp[i-1][j];
				dp[i][j]%=MOD;
			}else{
				dp[i][j] += dp[i-1][j-1] * 1LL * max(0,(j-(i>a)-(i>b)));
				dp[i][j] += dp[i-1][j+1] * 1LL * j;
				dp[i][j]%=MOD;
			}
		}
	}
	cout<<dp[n][1]<<'\n';
	
	
}

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49