Submission #114233

#	Time	Username	Problem	Language	Result	Execution time	Memory
114233		dorijanlendvaj	Palindromes (APIO14_palindrome)	C++14	8 / 100	1073 ms	12108 KiB

palindrome

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define x first
#define y second
#define pii pair<int,int>
#define pb push_back
#define eb emplace_back

using namespace std;
using namespace __gnu_pbds;

typedef long long int ll;
typedef unsigned long long int ull;
int MOD=1000000007;
int MOD2=998244353;
vector<int> bases;
const ll LLINF=1ll<<60;
const char en='\n';

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void yes() {cout<<"YES"<<en; exit(0);}
void no() {cout<<"NO"<<en; exit(0);}
inline int rund() {int x576363482791fuweh=rng();return abs(x576363482791fuweh)%RAND_MAX;}
template<class T>
void prVec(vector<T> w)
{
	cout<<w.size()<<endl;
	for (int i=0;i<int(w.size())-1;++i) cout<<w[i]<<' ';
	if (w.size()) cout<<w[w.size()-1]<<endl;
}

void M998()
{
	swap(MOD,MOD2);
}

ll raand()
{
	ll a=rund();
	a*=RAND_MAX;
	a+=rund();
    return a;
}

#define rand raand

ll raaand()
{
	return raand()*(MOD-7)+raand();
}

string to_upper(string a)
{
	for (int i=0;i<(int)a.size();++i) if (a[i]>='a' && a[i]<='z') a[i]-='a'-'A';
	return a;
}

string to_lower(string a)
{
	for (int i=0;i<(int)a.size();++i) if (a[i]>='A' && a[i]<='Z') a[i]+='a'-'A';
	return a;
}

ll sti(string a)
{
	ll k=0;
	for (int i=0;i<(int)a.size();++i)
	{
		k*=10;
		k+=a[i]-'0';
	}
	return k;
}

string its(ll k)
{
	if (k==0) return "0";
	string a;
	while (k)
	{
		a.push_back((k%10)+'0');
		k/=10;
	}
	reverse(a.begin(),a.end());
	return a;
}

ll min(ll a,int b)
{
	if (a<b) return a;
	return b;
}

ll min(int a,ll b)
{
	if (a<b) return a;
	return b;
}

ll max(ll a,int b)
{
	if (a>b) return a;
	return b;
}

ll max(int a,ll b)
{
	if (a>b) return a;
	return b;
}

ll gcd(ll a,ll b)
{
	if (b==0) return a;
	return gcd(b,a%b);
}

ll lcm(ll a,ll b)
{
	return a/gcd(a,b)*b;
}

template<class T,class K>
pair<T,K> mp(T a,K b)
{
	return make_pair(a,b);
}

inline int mult(ll a,ll b)
{
	return (a*b)%MOD;
}

inline int pot(int n,int k)
{
	if (k==0) return 1;
	ll a=pot(n,k/2);
	a=mult(a,a);
	if (k%2) return mult(a,n);
	else return a;
}

int divide(int a,int b)
{
	return mult(a,pot(b,MOD-2));
}

inline int sub(int a,int b)
{
	if (a-b>=0) return a-b;
	return a-b+MOD;
}

inline int add(int a,int b)
{
	if (a+b>=MOD) return a+b-MOD;
	return a+b;
}

bool prime(ll a)
{
	if (a==1) return 0;
	for (int i=2;i<=round(sqrt(a));++i)
	{
		if (a%i==0) return 0;
	}
	return 1;
}

ll has(string x)
{
	ll h1=0,h2=0;
	x=to_lower(x);
	for (char a: x)
	{
		h1*=bases[0];
		h1+=a-'a';
		h1%=bases[3];
		h2*=bases[1];
		h2+=a-'a';
		h2%=bases[4];
	}
	return h1*(MOD+13893829)+h2;
}

const int N=300010,MAGIC=15;
int n,prh1[N],prh2[N],po1[N],po2[N],sufa[N],c[N],rev1[N],rev2[N],inv1[N],inv2[N],po[N];
string h;
bool use2Hash=1;
int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};

bool equal(int i1,int i2,int l)
{
	int z=prh1[i1+l]-prh1[i2+l];
	if (z<0) z+=MOD;
	bool v1=(z==((po1[l]*1ll*((prh1[i1]-prh1[i2]+MOD)))%MOD));
	if (v1 && use2Hash)
	{
		return (((prh2[i1+l]-prh2[i2+l]+MOD2)%MOD2)==((po2[l]*1ll*(prh2[i1]-prh2[i2]+MOD2))%MOD2));
	}
	else return v1;
}

bool cmp(int i,int j)
{
	int lo=0,hi=min(n-j,n-i);
	if (hi>MAGIC*2 && !equal(i,j,MAGIC)) hi=MAGIC;
	while (lo<hi)
	{
		int mid=(lo+hi+1)/2;
		if (equal(i,j,mid)) lo=mid;
		else hi=mid-1;
	}
	if (i+lo==n) return 1;
	if (j+lo==n) return 0;
	return h[i+lo]<h[j+lo];
}

inline int addToHash(int prev,int nex,int ba,int mo)
{
	return (prev*1ll*ba+nex)%mo;
}

int get1(int l,int r)
{
	return (prh1[r]+(MOD-prh1[l])*1ll*po1[r-l])%MOD;
}

int get2(int l,int r)
{
	return (prh2[r]+(MOD2-prh2[l])*1ll*po2[r-l])%MOD2;
}

bool isPalindrome(int l,int r)
{
	int h1=(prh1[r]+(MOD-prh1[l])*1ll*po1[r-l])%MOD;
	int r1=rev1[r]-rev1[l];
	if (r1<0) r1+=MOD;
	r1=(r1*1ll*inv1[l])%MOD;
	if (h1==r1 && use2Hash)
	{
		h1=(prh2[r]+(MOD2-prh2[l])*1ll*po2[r-l])%MOD2;
		r1=rev2[r]-rev2[l];
		if (r1<0) r1+=MOD2;
		//cout<<h1<<' '<<r1<<' '<<rev2[r]<<' '<<rev2[l]<<' ';
		r1=(r1*1ll*inv2[l])%MOD2;
		//cout<<r1<<endl;
	}
	return h1==r1;
}

void mysort(int l,int r)
{
	if (l>=r) return;
	int mid=(l+r)/2;
	mysort(l,mid);
	mysort(mid+1,r);
	//cout<<l<<' '<<mid<<' '<<r<<endl;
	//for (int i=0;i<n;++i) cout<<sufa[i]<<' ';
	//cout<<endl;
	int x=l,y=mid+1,i=0;
	while (x!=mid+1 && y!=r+1)
	{
		if (cmp(sufa[x],sufa[y])) c[i]=sufa[x],++x;
		else c[i]=sufa[y],++y;
		++i;
	}
	if (x==mid+1)
	{
		while (y!=r+1) c[i]=sufa[y],++y,++i;
	}
	else
	{
		while (x!=mid+1) c[i]=sufa[x],++x,++i;
	}
	for (int i=l;i<=r;++i) sufa[i]=c[i-l];
}

gp_hash_table<int,bool> hap;
vector<pair<pii,int>> v; //hash, length, app in suf

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	//for (int i=0;i<10;++i) bases.push_back(rand()%(MOD-13893829)[phone]);
	bases.pb(5);
	bases.pb(7);
	cin>>h;
	//for (int i=0;i<300000;++i) h.pb(rand()%26+'a');
	n=h.size();
	for (int i=0;i<n;++i) prh1[i+1]=addToHash(prh1[i],h[i]-'a'+1,bases[0],MOD),prh2[i+1]=addToHash(prh2[i],h[i]-'a'+1,bases[1],MOD2);
	po1[0]=po2[0]=1;
	for (int i=1;i<=n;++i) po1[i]=(po1[i-1]*1ll*bases[0])%MOD,po2[i]=(po2[i-1]*1ll*bases[1])%MOD2;
	for (int i=0;i<n;++i) rev1[i+1]=(rev1[i]+(h[i]-'a'+1)*1ll*po1[i])%MOD,rev2[i+1]=(rev2[i]+(h[i]-'a'+1)*1ll*po2[i])%MOD2;
	inv1[0]=inv2[0]=1;
	inv1[1]=divide(1,bases[0]);
	swap(MOD,MOD2);
	inv2[1]=divide(1,bases[1]);
	swap(MOD,MOD2);
	for (int i=2;i<=n;++i) inv1[i]=(inv1[i-1]*1ll*inv1[1])%MOD,inv2[i]=(inv2[i-1]*1ll*inv2[1])%MOD2;
	for (int i=0;i<n;++i) sufa[i]=i;
	mysort(0,n-1);
	for (int i=0;i<n;++i) po[sufa[i]]=i;
	//cout<<"tu"<<endl;
	//for (int i=0;i<n;++i) cout<<sufa[i];
	//cout<<endl;
	for (int i=0;i<n;++i)
	{
		int lo=0,hi=min(i,n-i-1);
		if (hi>MAGIC*2 && !isPalindrome(i-MAGIC,i+MAGIC+1)) hi=MAGIC;
		while (lo<hi)
		{
			int mid=(lo+hi+1)/2;
			if (!isPalindrome(i-mid,i+mid+1)) hi=mid-1;
			else lo=mid;
		}
		int lo1=0,hi1=lo+1;
		while (lo1<hi1)
		{
			int mid=(lo1+hi1)/2;
			if (lo1+hi1==-1) --mid;
			if (hap[get1(i-mid,i+mid+1)]) lo1=mid+1;
			else hi1=mid;
		}
		for (int j=lo1;j<=lo;++j)
		{
			int a=get1(i-j,i+j+1);
			hap[get1(i-j,i+j+1)]=1;
			v.pb({{a,j*2+1},i-j});
		}
	}
	for (int i=1;i<n;++i)
	{
		int lo=-1,hi=min(i-1,n-i-1);
		if (hi>MAGIC*2 && !isPalindrome(i-MAGIC-1,i+MAGIC+1)) hi=MAGIC;
		while (lo<hi)
		{
			int mid=(lo+hi+1)/2;
			if (!isPalindrome(i-mid-1,i+mid+1)) hi=mid-1;
			else lo=mid;
		}
		int lo1=0,hi1=lo+1;
		while (lo1<hi1)
		{
			int mid=(lo1+hi1)/2;
			if (hap[get1(i-mid-1,i+mid+1)]) lo1=mid+1;
			else hi1=mid;
		}
		//cout<<i<<' '<<lo<<' '<<lo1<<' '<<get1(i-lo1,i-lo1+1)<<endl;
		for (int j=lo1;j<=lo;++j)
		{
			int a=get1(i-j-1,i+j+1);
			hap[get1(i-j-1,i+j+1)]=1;
			v.pb({{a,j*2+2},i-j-1});
		}
	}
	ll ans=0;
	for (auto a: v)
	{
		int hash=a.x.x,len=a.x.y,posSuf=po[a.y];
		int lo=0,hi=posSuf;
		while (lo<hi)
		{
			int mid=(lo+hi)/2;
			if (n-sufa[mid]<len || get1(sufa[mid],sufa[mid]+len)!=hash) lo=mid+1;
			else hi=mid;
		}
		int lo1=posSuf,hi1=n-1;
		while (lo1<hi1)
		{
			int mid=(lo1+hi1+1)/2;
			if (n-sufa[mid]<len || get1(sufa[mid],sufa[mid]+len)!=hash) hi1=mid-1;
			else lo1=mid;
		}
		ans=max(ans,len*1ll*(lo1-lo+1));
	}
	cout<<ans;
}

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