#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int nx=1e6+5, mod=1e9+7;
ll n, sz, dp[nx], dp2[nx], p[nx], val, val2, ans1=-1, ans2=-1;
string s1, s2;
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>s1;
p[0]=1;
for (int i=1; i<nx; i++) p[i]=(p[i-1]*26)%mod;
sz=n/2;
if (n%2==0)
{
cout<<"NOT POSSIBLE";
return 0;
}
s2.resize(n);
for (int i=0; i<sz+1; i++) s2[i]=s1[i+sz];
for (int i=sz+1; i<n; i++) s2[i]=s1[i-sz-1];
for (int i=sz+1; i<n; i++) val=(val+(s1[i]-'A')*p[i-sz-1])%mod;
for (int i=1; i<=sz+1; i++) dp[i]=(dp[i-1]+(s1[i-1]-'A')*p[i-1])%mod;
for (int i=sz+1; i>=1; i--) dp2[i]=(dp2[i+1]+(s1[i-1]-'A')*p[i-2])%mod;
for (int i=0; i<=sz; i++) if (dp[i]+dp2[i+2]==val) ans1=i;
for (int i=sz+1; i<n; i++) val2=(val2+(s2[i]-'A')*p[i-sz-1])%mod;
for (int i=1; i<=sz+1; i++) dp[i]=(dp[i-1]+(s2[i-1]-'A')*p[i-1])%mod;
for (int i=sz+1; i>=1; i--) dp2[i]=(dp2[i+1]+(s2[i-1]-'A')*p[i-2])%mod;
for (int i=1; i<=sz; i++) if (dp[i]+dp2[i+2]==val2) ans2=i;
if (ans1==-1&&ans2==-1)
{
cout<<"NOT POSSIBLE";
return 0;
}
if (ans1!=-1&&ans2==-1)
{
for (int i=sz+1; i<n; i++) cout<<s1[i];
return 0;
}
if (ans1==-1&&ans2!=-1)
{
for (int i=sz+1; i<n; i++) cout<<s2[i];
return 0;
}
if (ans1!=-1&&ans2!=-1&&val==val2)
{
for (int i=sz+1; i<n; i++) cout<<s2[i];
return 0;
}
cout<<"NOT UNIQUE";
}
/*
7
ABCAXBC
*/
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
7 ms |
8796 KB |
Output is correct |
| 2 |
Correct |
7 ms |
8836 KB |
Output is correct |
| 3 |
Correct |
6 ms |
9048 KB |
Output is correct |
| 4 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 5 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 6 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 7 |
Correct |
6 ms |
8840 KB |
Output is correct |
| 8 |
Correct |
7 ms |
8796 KB |
Output is correct |
| 9 |
Correct |
6 ms |
8840 KB |
Output is correct |
| 10 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 11 |
Correct |
6 ms |
8828 KB |
Output is correct |
| 12 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 13 |
Correct |
6 ms |
8764 KB |
Output is correct |
| 14 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 15 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 16 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 17 |
Correct |
7 ms |
8796 KB |
Output is correct |
| 18 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 19 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 20 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 21 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 22 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 23 |
Correct |
7 ms |
8660 KB |
Output is correct |
| 24 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 25 |
Correct |
6 ms |
8836 KB |
Output is correct |
| 26 |
Correct |
6 ms |
8792 KB |
Output is correct |
| 27 |
Correct |
7 ms |
8836 KB |
Output is correct |
| 28 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 29 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 30 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 31 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 32 |
Correct |
7 ms |
8792 KB |
Output is correct |
| 33 |
Correct |
6 ms |
8792 KB |
Output is correct |
| 34 |
Correct |
7 ms |
8796 KB |
Output is correct |
| 35 |
Correct |
6 ms |
8836 KB |
Output is correct |
| 36 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 37 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 38 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 39 |
Correct |
6 ms |
8844 KB |
Output is correct |
| 40 |
Correct |
6 ms |
8792 KB |
Output is correct |
| 41 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 42 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 43 |
Correct |
6 ms |
8796 KB |
Output is correct |
| 44 |
Incorrect |
6 ms |
8796 KB |
Output isn't correct |
| 45 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
64 ms |
28736 KB |
Output is correct |
| 2 |
Correct |
66 ms |
28740 KB |
Output is correct |
| 3 |
Incorrect |
46 ms |
27988 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
