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  1. #include <bits/stdc++.h>
  2. #define int long long
  3. using namespace std;
  4. const int N=25;
  5. int n;
  6. vector<pair<char,char>>v;
  7. char pos[N];
  8. int sum='A'+'B'+'C';
  9. void solve(int n,char from,char to,char g){
  10.     if(n==0)return ;
  11.     if(from==to){
  12.         solve(n-1,pos[n-1],to,sum-pos[n-1]-to);
  13.         return ;
  14.     }
  15.     solve(n-1,pos[n-1],g,sum-pos[n-1]-g);
  16.     v.push_back({from,to});
  17.     for(int i=1;i<=n-1;i++)pos[i]=g;
  18.     solve(n-1,g,to,from);
  19. }
  20. main()
  21. {
  22.     ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
  23.     cin>>n;
  24.     for(int i=1;i<=n;i++){
  25.         cin>>pos[i];
  26.     }
  27.     while(n>0&&pos[n]=='C')n--;
  28.     if(n==0)return cout<<0,0;
  29.     solve(n,pos[n],'C',sum-'C'-pos[n]);
  30.     cout<<v.size()<<'\n';
  31.     for(auto x:v)cout<<x.first<<x.second<<'\n';
  32.     return 0;
  33. }
  34.  
Success #stdin #stdout 0s 5328KB
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https://ideone.com/swGuJG
language:
C++14 (gcc 8.3)
created:
3 hours ago
visibility:
public

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