Submission #263264

#	Time	Username	Problem	Language	Result	Execution time	Memory
263264		blackyuki	Palindromes (APIO14_palindrome)	C++14	0 / 100	1091 ms	27456 KiB

palindrome

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n)  for(long long i=0;i<(long long)(n);i++)
#define REP(i,k,n) for(long long i=k;i<(long long)(n);i++)
#define all(a) a.begin(),a.end()
#define pb emplace_back
#define eb emplace_back
#define lb(v,k) (lower_bound(all(v),k)-v.begin())
#define ub(v,k) (upper_bound(all(v),k)-v.begin())
#define fi first
#define se second
#define pi M_PI
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T,vector<T>,greater<T>>
#define dame(a) {out(a);return 0;}
#define decimal cout<<fixed<<setprecision(15);
#define dupli(a) {sort(all(a));a.erase(unique(all(a)),a.end());}
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> PP;
typedef tuple<ll,ll,ll,ll> PPP;
typedef multiset<ll> S;
using vi=vector<ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vvvvi=vector<vvvi>;
using vp=vector<P>;
using vvp=vector<vp>;
using vb=vector<bool>;
using vvb=vector<vb>;
const ll inf=1001001001001001001;
const ll INF=1001001001;
const ll mod=1000000007;
const double eps=1e-10;
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outp(T a){cout<<'('<<a.fi<<','<<a.se<<')'<<'\n';}
template<class T> void outvp(T v){rep(i,v.size())cout<<'('<<v[i].fi<<','<<v[i].se<<')';cout<<'\n';}
template<class T> void outvvp(T v){rep(i,v.size())outvp(v[i]);}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){rep(i,v.size())outv(v[i]);}
template<class T> bool isin(T x,T l,T r){return (l)<=(x)&&(x)<=(r);}
template<class T> void yesno(T b){if(b)out("yes");else out("no");}
template<class T> void YesNo(T b){if(b)out("Yes");else out("No");}
template<class T> void YESNO(T b){if(b)out("YES");else out("NO");}
template<class T> void noyes(T b){if(b)out("no");else out("yes");}
template<class T> void NoYes(T b){if(b)out("No");else out("Yes");}
template<class T> void NOYES(T b){if(b)out("NO");else out("YES");}
void outs(ll a,ll b){if(a>=inf-100)out(b);else out(a);}
ll gcd(ll a,ll b){if(b==0)return a;return gcd(b,a%b);}
ll modpow(ll a,ll b){ll res=1;a%=mod;while(b){if(b&1)res=res*a%mod;a=a*a%mod;b>>=1;}return res;}

vi manacher(string &s){
    int i=0,j=0;
    vi res(s.size());
    while(i<s.size()){
        while(i-j>=0&&i+j<s.size()&&s[i-j]==s[i+j])j++;
        res[i]=j;
        int k=1;
        while(i-k>=0&&k+res[i-k]<j){
            res[i+k]=res[i-k];
            k++;
        }
        i+=k;j-=k;
    }
    return res;
}

ll N,k;
vi rankk,tmp;
bool co(int i,int j){
    if(rankk[i]!=rankk[j])return rankk[i]<rankk[j];
    int ri= i+k<=N ? rankk[i+k] : -1;
    int rj= j+k<=N ? rankk[j+k] : -1;
    return ri<rj;
}
vi make(string s){
    N=s.size();
    vi sa(N+1);
    rankk=vi(N+1);tmp=vi(N+1);
    rep(i,N+1){
        sa[i]=i;rankk[i]= i<N ? s[i] : -1;
    }
    for(k=1;k<=N;k*=2){
        sort(all(sa),co);
        tmp[sa[0]]=0;
        REP(i,1,N+1)tmp[sa[i]]=tmp[sa[i-1]]+(co(sa[i-1],sa[i])?1:0);
        rep(i,N+1)rankk[i]=tmp[i];
    }
    return sa;
}

int main(){
    string s;cin>>s;
    string t;
    rep(i,s.size()){
        if(i)t+='x';
        t+=s[i];
    }
    vi m=manacher(t);
    vp q;
    rep(i,m.size()){
        if(i&1)q.pb(i/2-m[i]/2+1,i/2+m[i]/2);
        else q.pb(i/2-(m[i]-1)/2,i/2+(m[i]-1)/2);
    }
    ll n=s.size();
    vi has(n+1);
    rep(i,n)has[i+1]=(has[i]*937+(s[i]-'a'+1))%mod;
    vi sa=make(s);
    vi rs(n+1);
    rep(i,n+1)rs[sa[i]]=i;
    ll ans=0;
    // outvp(q);outv(sa);outv(rs);outv(has);
    for(auto x:q){
        ll len=x.se-x.fi+1;
        ll to=rs[x.fi],ng=n+1;
        while(ng-to>1){
            ll md=(to+ng)/2;
            ll id=sa[md];
            if(id+len>n){ng=md;continue;}
            ll a=(has[x.se+1]-has[x.fi]+mod)%mod;
            ll b=(has[id+len]-has[id]+mod)%mod;
            if(x.fi<id)a=a*modpow(937,id-x.fi);
            else b=b*modpow(937,x.fi-id);
            if(a%mod==b%mod)to=md;
            else ng=md;
        }
        ll fr=rs[x.fi],ngg=0;
        while(fr-ngg>1){
            ll md=(fr+ngg)/2;
            ll id=sa[md];
            if(id+len>n){ngg=md;continue;}
            ll a=(has[x.se+1]-has[x.fi]*modpow(937,len)%mod+mod)%mod;
            ll b=(has[id+len]-has[id]*modpow(937,len)%mod+mod)%mod;
            // if(x.fi<id)a=a*modpow(937,id-x.fi);\else b=b*modpow(937,x.fi-id);
            // if(x==P(0,2)){out(md);outp(P(a,b));}
            if(a%mod==b%mod)fr=md;
            else ngg=md;
        }
        // if(x==P(0,2))outp(P(to,fr));
        chmax(ans,(to-fr+1)*len);
    }
    out(ans);
}

Compilation message (stderr)

palindrome.cpp: In function 'vi manacher(std::string&)':
palindrome.cpp:57:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |     while(i<s.size()){
      |           ~^~~~~~~~~
palindrome.cpp:58:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |         while(i-j>=0&&i+j<s.size()&&s[i-j]==s[i+j])j++;
      |                       ~~~^~~~~~~~~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27