Submission #1118235

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118235		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	29 ms	23132 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define run  ios_base::sync_with_stdio(false);cin.tie(0);
 
#define ll long long
#define pll pair<ll, ll>
#define ull unsigned ll
#define ld double
#define endl "\n"
#define pb push_back
#define fi first
#define se second
 
#define pi acos(-1)
#define N 2007
#define minimum -9223372036854775807
#define maximum -minimum
#define mod 1000000007
 
using namespace std;
using namespace __gnu_pbds;
template <class t>
using ordered_set=tree<t, null_type,less_equal<t>, rb_tree_tag,tree_order_statistics_node_update>;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

ll gcd(ll a, ll b)
{
	if(b==0)
		return a;
	return gcd(b, a%b);
}

ll lcm(ll a, ll b)
{
	return a/gcd(a, b)*b;
}

bool isprime(ll n)
{
	if(n==1)
		return 0;
	for(ll i=2; i*i<=n; i++)
	{
		if(n%i==0)
			return 0;
	}
	return 1;
}

ll binpow(ll a, ll b)
{
    a%=mod;
    ll res=1;
    while(b>0)
	{
        if(b%2==1)
            res=(res*a)%mod;
        a=(a*a)%mod;
        b/=2;
    }
    return res;
}

ll dp[N][N];

int main()
{
    run;
    ll n, cs, cf, fixed=0;
    cin>>n>>cs>>cf;
    dp[1][1]=1;
    for(ll i=2; i<=n; i++)
    {
    	fixed=0;
    	if(i>cs)
    		fixed++;
    	if(i>cf)
    		fixed++;
    	for(ll j=1; j<=i; j++)
    	{
    		if(i==cs || i==cf)
    		{
    			dp[i][j]=((dp[i][j]+dp[i-1][j-1])%mod+dp[i-1][j])%mod;
			}
			else
			{
				dp[i][j]=(dp[i][j]+(dp[i-1][j+1]*j)%mod)%mod;
				dp[i][j]=(dp[i][j]+(dp[i-1][j-1]*(j-fixed))%mod)%mod;
			}
		}
	}
	cout<<dp[n][1]<<endl;
}
// By Xanlar

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