Submission #1242400

#	Time	Username	Problem	Language	Result	Execution time	Memory
1242400		m.zeeshanrashid	Kangaroo (CEOI16_kangaroo)	C++20	100 / 100	45 ms	55112 KiB

kangaroo

#ifdef __AVX2__
#pragma GCC target "avx2"
#endif
#pragma GCC optimize "O3"
#pragma GCC optimize "unroll-loops"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
using namespace __gnu_pbds; 
using namespace std;
#define int long long
#define elif else if
#define all(l) begin(l),end(l)
#define rall(l) rbegin(l),rend(l)
#define append push_back
#define print(l) for(auto i:l) cout<<i<<' '; cout<<endl;
#define pprint(a,b) cout<<a<<' '<<b<<endl;
#define inp(l) for(auto &i:l) cin>>i;
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define pai make_pair
#define endl "\n"
#define pii pair<int,int>
#define fi first
#define se second
#define vec vector

const int mod1=998244353;
const int mod=1e9+7;
const int N=2e3+5;

int dp[N][N][3];

int iter=1,itera=1;
void solve(){
	int n,s,t;
	cin>>n>>s>>t;
	if(s<2 or t<2) dp[1][1][1]=1;
	else dp[1][1][0]=1;
	for(int i=1;i<n;i++){
		for(int j=1;j<=i;j++){
			if(i==s-1 or i==t-1){
				for(int k=0;k<2;k++){
					dp[i+1][j][k+1]+=dp[i][j][k];
					dp[i+1][j][k+1]%=mod;
					dp[i+1][j+1][k+1]+=dp[i][j][k];
					dp[i+1][j+1][k+1]%=mod;
				}
			}
			else{
				for(int k=0;k<3;k++){
					dp[i+1][j+1][k]+=dp[i][j][k]*(j-k+1);
					dp[i+1][j+1][k]%=mod;
					dp[i+1][j-1][k]+=dp[i][j][k]*(j-1);
					dp[i+1][j-1][k]%=mod;
				}
			}
		}
	}
	cout<<dp[n][1][2]<<endl;
}
signed main(){
	// freopen("","r",stdin);
	// freopen("","w",stdout);
	ios_base::sync_with_stdio(false);
	cin.tie(NULL); 
	cout.tie(NULL);
	// cin>>itera;
	for(iter=1;iter<=itera;iter++) solve();
}

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