using namespace std;
typedef long long ll;
vector<ll>pi;
void preFunc(string s)
{
ll len=s.size();
pi.resize(len+5);
pi[0]=0;
for(ll i=1;i<len;i++){
ll j=pi[i-1];
while(j>0&&s[i]!=s[j])j=pi[j-1];
if(s[i]==s[j])j++;
pi[i]=j;
}
}
int main()
{
ll t;
cin>>t;
string s;
while(t--){
cin>>s;
string p=s;
p+="#";
reverse(s.begin(),s.end());
p+=s;
ll len=p.size();
preFunc(p);
ll idx=0;
for(ll i=(ll)s.size();i<len;i++){
idx=max(idx,pi[i]);
}
for(ll i=idx-1;i>=0;i--){
cout<<p[i];
}
cout<<"\n";
}
return 0;
}
Code language: PHP (php)