Submission #1201683

#	Time	Username	Problem	Language	Result	Execution time	Memory
1201683		hashimali	Kangaroo (CEOI16_kangaroo)	C++20	100 / 100	33 ms	55112 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define endl '\n'
#define ld long double
#define pb push_back
#define pf push_front
#define mod 1'000'000'007
#define se second
#define fi first
#define all(ls) (ls).begin(),(ls).end()
#define int long long
using namespace std;
using namespace __gnu_pbds;
template<typename type>using ordered_set=tree<type,null_type,less<type>,rb_tree_tag,tree_order_statistics_node_update>;
template<typename type>using ordered_multiset=tree<type,null_type,less_equal<type>,rb_tree_tag,tree_order_statistics_node_update>;
const int N=2001;
int dp[N][N][3];
void solve(){
    int n,s,e;
    cin>>n>>s>>e;
    dp[1][1][(s==1)+(e==1)]=1;
    for(int i=2;i<n+1;i++)
        for(int j=1;j<i+1;j++)
            if((s==i)+(e==i)){
                dp[i][j][1]=(dp[i-1][j-1][0]+dp[i-1][j][0])%mod;
                dp[i][j][2]=(dp[i-1][j-1][1]+dp[i-1][j][1])%mod;
            }
            else{
                dp[i][j][0]=(dp[i-1][j+1][0]*j)%mod;
                dp[i][j][1]=(dp[i-1][j+1][1]*j)%mod;
                dp[i][j][2]=(dp[i-1][j+1][2]*j)%mod;
                if(j>=0)
                    dp[i][j][0]=(dp[i][j][0]+(dp[i-1][j-1][0]*j))%mod;
                if(j>=1)
                    dp[i][j][1]=(dp[i][j][1]+(dp[i-1][j-1][1]*(j-1)))%mod;
                if(j>=2)
                    dp[i][j][2]=(dp[i][j][2]+(dp[i-1][j-1][2]*(j-2)))%mod;
            }
    cout<<dp[n][1][2]%mod<<endl;
}
signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t=1;
    // cin>>t;
    for(int i=1;i<=t;i++){
        // cout<<"Scenario #"<<i<<":"<<" ";
        solve();
    }
}

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