#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, ans=-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) ans=i;
if (ans!=-1)
{
for (int i=sz+1; i<n; i++) cout<<s1[i];
return 0;
}
val=0;
for (int i=sz+1; i<n; i++) val=(val+(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=0; i<=sz; i++) if (dp[i]+dp2[i+2]==val) ans=i;
if (ans!=-1)
{
for (int i=sz+1; i<n; i++) cout<<s2[i];
return 0;
}
cout<<"NOT POSSIBLE";
}
/*
7
ABCAXBC
*/
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
7 ms |
8796 KB |
Output is correct |
2 |
Correct |
6 ms |
8792 KB |
Output is correct |
3 |
Correct |
7 ms |
8796 KB |
Output is correct |
4 |
Correct |
7 ms |
8796 KB |
Output is correct |
5 |
Correct |
7 ms |
8660 KB |
Output is correct |
6 |
Correct |
6 ms |
8612 KB |
Output is correct |
7 |
Correct |
8 ms |
8796 KB |
Output is correct |
8 |
Correct |
7 ms |
9048 KB |
Output is correct |
9 |
Correct |
7 ms |
8796 KB |
Output is correct |
10 |
Correct |
6 ms |
8832 KB |
Output is correct |
11 |
Correct |
6 ms |
8796 KB |
Output is correct |
12 |
Correct |
6 ms |
8844 KB |
Output is correct |
13 |
Correct |
6 ms |
8792 KB |
Output is correct |
14 |
Correct |
6 ms |
8796 KB |
Output is correct |
15 |
Correct |
6 ms |
8952 KB |
Output is correct |
16 |
Correct |
6 ms |
8796 KB |
Output is correct |
17 |
Correct |
6 ms |
8848 KB |
Output is correct |
18 |
Incorrect |
7 ms |
8792 KB |
Output isn't correct |
19 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
50 ms |
30836 KB |
Output is correct |
2 |
Correct |
48 ms |
30708 KB |
Output is correct |
3 |
Incorrect |
47 ms |
29872 KB |
Output isn't correct |
4 |
Halted |
0 ms |
0 KB |
- |