Submission #21830

#	Time	Username	Problem	Language	Result	Execution time	Memory
21830		ngkan146	Three Friends (BOI14_friends)	C++14	35 / 100	13 ms	44344 KiB

friends

#include <bits/stdc++.h>
using namespace std;
string s;
int n;
int ans = 0;
void no(){
   cout << "NOT POSSIBLE";
   exit(0);
}
int l[5000005],r[5000005], ansPOS;
vector <int> poss;
void check(){
   for(int i=n/2;i<n-1;i++){
      if (s[i-n/2] == s[i]) l[i] = l[i-1] + 1;
      else l[i] = - (int)1e9;
   }
   for(int i=n-1;i>n/2;i--)
      if (s[i-n/2-1] == s[i]) r[i] = r[i+1] + 1;
      else r[i] = - (int) 1e9;

   for(int i=n/2;i<n;i++){
      if (l[i-1] + r[i+1] == n/2) ans++, ansPOS = i, poss.push_back(i);
   }

   for(int i=0;i<n/2;i++){
      if (s[i] == s[i+n/2+1]) l[i] = (i ? l[i-1] : 0) + 1;
      else l[i] = -(int) 1e9;
   }
   r[n/2+1] = 0;
   for(int i=n/2;i>=1;i--){
      if (s[i] == s[i+n/2]) r[i] = r[i+1] + 1;
      else r[i] = -(int) 1e9;
   }
   for(int i=0;i<n/2;i++){
      if ((i?l[i-1]:0) + r[i+1] == n/2) ans++, ansPOS = i, poss.push_back(i);
   }
}
int main(){
   iostream::sync_with_stdio(0);
   cin >> n >> s;
   if (n%2==0) no();
   check();
   int cnt = 0;
   if (!ans) no();
   else{
      bool ok = 1;
      sort(poss.begin(),poss.end());
      for(int i=0;i<(int)poss.size()-1;i++){
         if (abs(poss[i]-poss[i+1]) != 1 || s[poss[i]]!=s[poss[i+1]]) ok = 0;
      }
      if (!ok) cout << "NOT UNIQUE";
      else{
         for(int i=0;i<n;i++) if (cnt<n/2 && i != ansPOS) cnt++, cout << s[i];
      }
   }
}

• Subtask 1: 35 / 35
• Subtask 2: 0 / 65