제출 #465463

#제출 시각아이디문제언어결과실행 시간메모리
465463Khizri캥거루 (CEOI16_kangaroo)C++17
0 / 100
1 ms332 KiB
#include <bits/stdc++.h>
using namespace std;
//------------------------------DEFINE------------------------------
//******************************************************************
#define IOS ios_base::sync_with_stdio(false); cin.tie(0),cout.tie(0)
#define ll long long
#define pb push_back		 
#define F first																 
#define S second 															 
#define INF 1e18
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define pii pair<int,int>
#define pll pair<ll,ll>
#define OK cout<<"Ok"<<endl;
#define MOD (ll)(1e9+7)
#define endl "\n"
//******************************************************************
//----------------------------FUNCTION------------------------------
//******************************************************************
ll gcd(ll a,ll b){
	if(a>b) swap(a,b);
	if(a==0) return a+b;
	return gcd(b%a,a);
}
ll lcm(ll a,ll b){
	return a/gcd(a,b)*b;
}
bool is_prime(ll n){
	ll k=sqrt(n);
	if(n==2) return true;
	if(n<2||n%2==0||k*k==n) return false;
	for(int i=3;i<=k;i+=2){
		if(n%i==0){
			return false;
		}
	}
	return true;
}
//*****************************************************************
//--------------------------MAIN-CODE------------------------------
const int mxn=2000+5;
ll t=1,n,l,r,dp[2][mxn][mxn];
void solve(){
	cin>>n>>l>>r;
	dp[0][1][l]=1;
	dp[1][1][l]=1;
	for(int i=2;i<=n;i++){
		for(int j=1;j<=n;j++){
			if(j==l||(i<n&&j==r)){
				continue;
			}
			for(int k=1;k<j;k++){
				if(k==r){
					continue;
				}
				dp[0][i][j]=(dp[1][i-1][k]+dp[0][i][j])%MOD;
			}
			for(int k=j+1;k<=n;k++){
				if(k==r){
					continue;
				}
				dp[1][i][j]=(dp[1][i][j]+dp[0][i-1][k])%MOD;
			}
		}
	}
	cout<<(dp[0][n][r]+dp[1][n][r])%MOD;
}
int main(){
	IOS;
	//cin>>t;
	while(t--){
		solve();
	}
	return 0;
}
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