Submission #1117339

#	Time	Username	Problem	Language	Result	Execution time	Memory
1117339		Tai_xiu	Kangaroo (CEOI16_kangaroo)	C++14	0 / 100	1 ms	336 KiB

kangaroo

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

#define ll long long
#define i128 int128
#define ii pair<int,int>
#define ld long double
#define vi vector<int>
#define vvi vector<vi>
#define vii vector<pair<int,int>>
#define FOR(i,a,b) for (int i=a;i<=b;i++)
#define FOR1(i,a,b,c) for (int i=a;i<=b;i+=c)
#define REP(i,a,b) for (int i=a;i>=b;i--)
#define REP1(i,a,b,c) for(int i=b;i>=a;i-=c)
#define endh '\n';
#define len(a) a.length()
#define pb(c) push_back(c)
#define elif else if
#define ppb() pop_back()
#define rong std::npos
#define all(c) (c.begin(),c.end())
#define Z int
#define R double
#define lcm(a,b) ((int) (a/__gcd(a,b))*b)
#define mk(a,b) make_pair(a,b)
Z dx4[]={-1,1,0,0};
Z dy4[]={0,0,1,-1};
string co="YES",khong="NO";
const int mod=1e9+7;
Z dp[2003][2003];

Z mul(Z a,Z b)
{
    ll tam=a;
    tam=a*1ll*b;
    tam%=mod;
    return tam;
}
void add(Z &a,Z b)
{
    if ((a+=b)>=mod) a-=mod;
}
Z n,s,t;
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    cin>>n>>s>>t;
    dp[1][1]=1;
    FOR(i,2,n){
        FOR(j,1,n){
            if (i==s || i==t){
                add(dp[i][j+1],dp[i-1][j]);
                add(dp[i][j],dp[i-1][j]);
            }
            else{
                add(dp[i][j],mul(dp[i-1][j-1],j+1-(i>s)-(i>t)));
                add(dp[i][j-1],mul(dp[i-1][j],j-1));
            }
        }
    }
    cout<<dp[n][1];
}

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