Submission #356832

#	Time	Username	Problem	Language	Result	Execution time	Memory
356832		Kerim	Palindromes (APIO14_palindrome)	C++17	100 / 100	683 ms	51536 KiB

palindrome

#include "bits/stdc++.h"
#define MAXN 300009
#define INF 1000000007
#define mp(x,y) make_pair(x,y)
#define all(v) v.begin(),v.end()
#define pb(x) push_back(x)
#define wr cout<<"----------------"<<endl;
#define ppb() pop_back()
#define tr(ii,c) for(__typeof((c).begin()) ii=(c).begin();ii!=(c).end();ii++)
#define ff first
#define ss second
#define my_little_dodge 46
#define debug(x)  cerr<< #x <<" = "<< x<<endl;
using namespace std;
 
typedef long long ll;
typedef pair<int,int> PII;
template<class T>bool umin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool umax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
const int LOG=20;
int S[MAXN][LOG],ord[MAXN],lcp[MAXN],rad[MAXN<<1],ext[MAXN],vis[MAXN],n;
pair<PII,int> C[MAXN],H[MAXN];
char s[MAXN],tmp[MAXN<<1];
void fastsort(){
	memset(vis,0,sizeof(vis));
	for(int i=1;i<=n;i++)
		vis[C[i].ff.ss]++;
	for(int i=1;i<MAXN;i++)
		vis[i]+=vis[i-1];
	for(int i=n;i>=1;i--)
		H[vis[C[i].ff.ss]--]=C[i];
	memset(vis,0,sizeof(vis));
	for(int i=1;i<=n;i++)
		vis[H[i].ff.ff]++;
	for(int i=1;i<MAXN;i++)
		vis[i]+=vis[i-1];	
	for(int i=n;i>=1;i--)
		C[vis[H[i].ff.ff]--]=H[i];	
}
int ata[MAXN],sz[MAXN];
int tap(int x){
	if(ata[x]==x)return x;
	return ata[x]=tap(ata[x]);
}	
void merge(int x,int y){
	if((x=tap(x))==(y=tap(y)))
		return;
	if(ext[x]<ext[y])swap(x,y);
	ata[y]=x;sz[x]+=sz[y];ext[x]+=ext[y];
}
int main(){
    //freopen("file.in", "r", stdin);
    scanf("%s",s+1);
    n=strlen(s+1);
    for(int i=1;i<=n;i++)
    	S[i][0]=s[i]-'a'+1;
    for(int j=1;j<LOG;j++){
    	for(int i=1;i<=n;i++)
			C[i]=mp(mp(S[i][j-1],(i+(1<<(j-1))<=n?S[i+(1<<(j-1))][j-1]:0)),i);
		//sort(c+1,c+n+1,cmp);
		fastsort();
		for(int i=1;i<=n;i++)
			S[C[i].ss][j]=S[C[i-1].ss][j]+(C[i].ff!=C[i-1].ff);	
    }
    for(int i=1;i<=n;i++)
    	ord[S[i][LOG-1]]=i;
    vector<pair<int,PII> >v;
    vector<PII>g;
    for(int i=1;i<n;i++){
    	int a=ord[i],b=ord[i+1];
		for(int j=LOG-1;j>=0;j--)
			if(a<=n and b<=n and S[a][j]==S[b][j])
				a+=(1<<j),b+=(1<<j),lcp[i]+=(1<<j);
		v.pb(mp(lcp[i],mp(ord[i],ord[i+1])));
    }
    sort(all(v),greater<pair<int,PII>>());
	for(int i=0;i<2*n+1;i++)tmp[i]='#';
	for(int i=0;i<n;i++)tmp[i*2+1]=s[i+1];
	for(int i=0,j=0,k;i<n*2+1;i+=k){
		while(i-j>=0&&i+j<n*2+1&&tmp[i-j]==tmp[i+j])j++;
		rad[i]=j;k=1;
		while(rad[i-k]<rad[i]-k)rad[i+k]=rad[i-k],k++;
		j=max(0,j-k);
	}
    //odd
	for(int i=1;i<=n;i++)g.pb(mp(rad[i*2-1]/2,i));
	sort(all(g),greater<PII>());
	int p=0;ll ans=0;
	for(int i=1;i<=n;i++)ata[i]=i,sz[i]=0,ext[i]=1;
	for(int i=0;i<n;i++){
		while(p<int(v.size()) and v[p].ff>=g[i].ff)
			merge(v[p].ss.ff,v[p].ss.ss),p++;
		sz[tap(g[i].ss)]++;
		umax(ans,sz[tap(g[i].ss)]*1LL*(g[i].ff*2-1));
	}
	//even
	g.clear();
	for(int i=1;i<n;i++)g.pb(mp(rad[i*2]/2,i+1));
	sort(all(g),greater<PII>());p=0;
	for(int i=1;i<=n;i++)ata[i]=i,sz[i]=0,ext[i]=1;
	for(int i=0;i<n-1;i++){
		while(p<int(v.size()) and v[p].ff>=g[i].ff)
			merge(v[p].ss.ff,v[p].ss.ss),p++;
		sz[tap(g[i].ss)]++;
		umax(ans,sz[tap(g[i].ss)]*1LL*(g[i].ff*2));
	}
	printf("%lld\n",ans);
	return 0;
}

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:53:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   53 |     scanf("%s",s+1);
      |     ~~~~~^~~~~~~~~~

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