Submission #558426

#	Time	Username	Problem	Language	Result	Execution time	Memory
558426		andreast12	Kangaroo (CEOI16_kangaroo)	C++17	0 / 100	1 ms	340 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define pb push_back
const int mod=1e9+7, maxn=1e4+5;
int n, s, e;
ll res, memo[100][10][2];

ll dp(int mask, int node, int arah) {
	if(__builtin_popcount(mask)==n-1) {
		for(int i=0; i<n; i++) {
			if(((1<<i)&mask)==0) {
				if(i+1==e) return 1;
				else return 0;
			}
		}
	}
	if(memo[mask][node][arah]!=-1) return memo[mask][node][arah];
	ll ans=0;
	if(arah) {
		for(int i=node+1; i<=n; i++) {
			if(((1<<(i-1))&mask)==0) ans=(dp(mask|(1<<(i-1)), i, 1-arah)+ans)%mod;
		}
	} else {
		for(int i=node-1; i>0; i--) {
			if(((1<<(i-1))&mask)==0) ans=(dp(mask|(1<<(i-1)), i, 1-arah)+ans)%mod;
		}
	}
	memo[mask][node][arah]=ans;
	return ans;
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(NULL);
	cin >> n >> s >> e;
	memset(memo, -1, sizeof(memo));
	res=dp(1<<(s-1), s, 0);
	memset(memo, -1, sizeof(memo));
	res=(res+dp(1<<(s-1), s, 1))%mod;
	cout << res << '\n';
}

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