Submission #315757

#	Time	Username	Problem	Language	Result	Execution time	Memory
315757		fadi57	Kangaroo (CEOI16_kangaroo)	C++14	0 / 100	50 ms	94200 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
const int mx=2000;
const int mod=1000000007;
typedef long long ll;
int n,m;
int st,en;
//(i,x,state);
map<int,int>mp;
ll dp[mx][mx][3];
ll solve(int i,int x,int dir){
    if(i==en){
       if(x==n){
        return 1;}
        return 0;
    }
   ll &ret=dp[i][x][dir];
  if(ret!=-1){return ret;}
     ret=0;
    if(dir==0){
        for(int j=i+1;j<=n;j++){
            if(mp[j]){continue;}
            
            mp[j]=1;
            ret=(ret+solve(j,x+1,dir^1))%mod;
            mp[j]=0;
        }
        
    }else{
         for(int j=i-1;j>=1;j--){
            if(mp[j]){continue;}
            mp[j]=1;
            ret=(ret+solve(j,x+1,dir^1))%mod;
            mp[j]=0;
        }
    }return ret%mod;
    
}
int main() {
   
  cin>>n>>st>>en;
  for(int i=0;i<mx;i++){
      for(int j=0;j<mx;j++){
          dp[i][j][0]=dp[i][j][1]=-1;
      }
  }
  
  mp[st]=1;
  cout<<(solve(st,1,0)+solve(st,1,1))%mod;

 
}

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