Submission #308921

#	Time	Username	Problem	Language	Result	Execution time	Memory
308921		arnold518	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	71 ms	32120 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;

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

const int MAXN = 2000;
const ll MOD = 1e9+7;

int N, S, E;

ll dp[MAXN+10][MAXN+10];

ll solve(int pos, int comp)
{
	if(pos==N+1)
	{
		if(comp==1) return 1;
		else return 0;
	}
	ll &ret=dp[pos][comp];
	if(ret!=-1) return ret;

	ret=0;

	if(pos==S)
	{
		ret+=solve(pos+1, comp);
		ret+=solve(pos+1, comp+1);
	}
	else if(pos==E)
	{
		ret+=solve(pos+1, comp);
		ret+=solve(pos+1, comp+1);
	}
	else if(pos<S)
	{
		if(comp>=2) ret+=(comp-1)*solve(pos+1, comp-1);
		ret+=(comp+1)*solve(pos+1, comp+1);
	}
	else if(pos<E)
	{
		if(comp>=2) ret+=(comp-1)*solve(pos+1, comp-1);
		ret+=(comp)*solve(pos+1, comp+1);	
	}
	else
	{
		if(comp>=2) ret+=(comp-1)*solve(pos+1, comp-1);
		ret+=(comp-1)*solve(pos+1, comp+1);		
	}
	ret%=MOD;
	//printf("%d %d : %lld\n", pos, comp, ret);
	return ret;
}

int main()
{
	scanf("%d%d%d", &N, &S, &E); if(S>E) swap(S, E);
	memset(dp, -1, sizeof(dp));
	printf("%lld\n", solve(1, 0));

}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:59:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   59 |  scanf("%d%d%d", &N, &S, &E); if(S>E) swap(S, E);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~

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