Submission #249774

#	Time	Username	Problem	Language	Result	Execution time	Memory
249774		mraron	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	25 ms	23040 KiB

kangaroo

#include<iostream>
#include<vector>
#include<map>
#include<set>
#include<cassert>
#include<cassert>
#include<unordered_map>
#include<unordered_set>
#include<functional>
#include<queue>
#include<stack>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<sstream>
#include<iomanip>
#include<cstdio>
#include<cstdlib>
#include<numeric>
#include<random>
#include<chrono>
#include<bitset>
using namespace std;

#define all(x) (x).begin(), (x).end()
#define pb push_back
#define xx first
#define yy second
#define sz(x) (int)(x).size()
#define gc getchar
#define IO ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define mp make_pair

#ifndef ONLINE_JUDGE
#  define LOG(x) (cerr << #x << " = " << (x) << endl)
#else
#  define LOG(x) ((void)0)
#endif

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

const double PI=acos(-1);
const ll INF = 1LL<<62;
const ll MINF = -(1LL<<62);

template<typename T> T getint() {
	T val=0;
	char c;
	
	bool neg=false;
	while((c=gc()) && !(c>='0' && c<='9')) {
		neg|=c=='-';
	}

	do {
		val=(val*10)+c-'0';
	} while((c=gc()) && (c>='0' && c<='9'));

	return val*(neg?-1:1);
}

//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); uniform_int_distribution<int>(0, n-1)(rng)


const ll mod=1e9+7;

ll dp[2001][2001];

int main() {
	IO;
	ll n,st,en;
	cin>>n>>st>>en;
	dp[1][1]=1;
	for(ll i=2;i<=n;++i) {
		for(ll j=1;j<=i;++j) {
			if(i==st || i==en) {
				dp[i][j]=(dp[i-1][j]+dp[i-1][j-1])%mod;
			}else {
				dp[i][j]=(dp[i][j]+dp[i-1][j+1]*j)%mod;
				dp[i][j]=(dp[i][j]+dp[i-1][j-1]*(j-(i>=st)-(i>=en)))%mod;
			}
		}
	}
	//~ LOG(dp[1][1]);
	//~ LOG(dp[2][2]);
	//~ LOG(dp[3][1]);
	//~ LOG(dp[3][2]);
	//~ LOG(dp[3][3]);
	//~ LOG(dp[4][1]);
	//~ LOG(dp[4][2]);
	//~ LOG(dp[4][3]);
	//~ LOG(dp[4][4]);
	cout<<dp[n][1]<<"\n";
	
	return 0;
}

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