Submission #917180

#	Time	Username	Problem	Language	Result	Execution time	Memory
917180		KiaRez	Kangaroo (CEOI16_kangaroo)	C++17	6 / 100	1 ms	2652 KiB

kangaroo

/*
    IN THE NAME OF GOD
*/
#include <bits/stdc++.h>

// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef long double ld;

#define F                                      first
#define S                                      second
#define Mp                                     make_pair
#define pb                                     push_back
#define pf                                     push_front
#define size(x)                                ((ll)x.size())
#define all(x)                                 (x).begin(),(x).end()
#define kill(x)		                           cout << x << '\n', exit(0);
#define fuck(x)                                cout << "(" << #x << " , " << x << ")" << endl
#define endl                                   '\n'

const int N = 3e5+23, lg = 18;
ll Mod = 1e9+7; //998244353;

inline ll MOD(ll a, ll mod=Mod) {a%=mod; (a<0)&&(a+=mod); return a;}
inline ll poww(ll a, ll b, ll mod=Mod) {
    ll ans = 1;
    a=MOD(a, mod);
    while (b) {
        if (b & 1) ans = MOD(ans*a, mod);
        b >>= 1;
        a = MOD(a*a, mod);
    }
    return ans;
}

int ln, s, f, mark[2005][2005][2];
ll mp[2005][2005][2];

ll calc(int n, int i, int j, int flg=0) {
	if(min(i, j)<=0 || max(i, j)>n || i==j) return 0;
	if(n==2) {
		if(i<j&&flg==0) return 1;
		if(i>j&&flg==1) return 1;
		return 0;
	}
	if(i > j) {
		if((n-1)%2 == 1) return calc(n, j, i, 1-flg);
		return calc(n, j, i, flg);
	}

	if(mark[n][i][flg] == 1) return mp[n][i][flg];
	
	ll res = 0;
	if(flg == 0) {
		if(i==j-1) {
			for(int k=i+1; k<=n-1; k++) res = MOD(res + calc(n-1, k, j-1, 1));
		} else {
			res = MOD(calc(n, i+1, j, 0) + calc(n-1, i, j-1, 1));
		}
	} else {
		res = MOD(res + calc(n, i-1, j, 1) + calc(n-1, i-1, j-1, 0));
	}
	mp[n][i][flg] = res, mark[n][i][flg] = 1;
	return res;
}

int main () {
	ios_base::sync_with_stdio(false), cin.tie(0);

	cin>>ln>>s>>f;
	//fuck(calc(3, 3, 2, 1));
	//fuck(calc(ln, s, f, 0));
	cout<<MOD(calc(ln, s, f, 0) + calc(ln, s, f, 1));

	return 0;
}

• Subtask 1: 6 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49