Submission #9855

#	Time	Username	Problem	Language	Result	Execution time	Memory
9855		dohyun0324	Palindromes (APIO14_palindrome)	C++98	100 / 100	748 ms	43572 KiB

palindrome

#include<stdio.h>
#include<algorithm>
#include<string.h>
#define M 300010
using namespace std;
long long dap;
int n,SA[20][M],arr[M],order[M],lcp[M],d[M*2],arr2[M*2],len[M],top,ch[30];
int p1[M],p2[M],st1[M],st2[M];
char a[M],s[M*2],b[M*2];
struct data
{
    int x,y,p;
    bool operator<(const data&r)const{
        if(x==r.x) return y<r.y;
        return x<r.x;
    }
}L[M];
void Suffix_Array()
{
    int i,j,k=1,cnt;
    for(i=1;i<=n;i++) ch[a[i]-'a'+1]=1;
    for(i=1;i<=26;i++) ch[i]+=ch[i-1];
    for(i=1;i<=n;i++) SA[0][i]=ch[a[i]-'a'+1];
    for(i=1;;i++)
    {
        if(k>n-1) break;
        for(j=1;j<=n;j++)
        {
            L[j].x=SA[i-1][j];
            if(j+k<=n) L[j].y=SA[i-1][j+k];
            else L[j].y=-1;
            L[j].p=j;
        }
        sort(L+1,L+n+1);
        cnt=0;
        for(j=1;j<=n;j++)
        {
            if(L[j].x!=L[j-1].x) SA[i][L[j].p]=++cnt;
            else if(L[j].y!=L[j-1].y) SA[i][L[j].p]=++cnt;
            else SA[i][L[j].p]=cnt;
        }
        k*=2;
    }
    for(j=1;j<=n;j++) arr[j]=SA[i-1][j];
}
void LCP()
{
    int i,j,k=0;
    for(i=1;i<=n;i++) order[arr[i]]=i;
    for(i=1;i<=n;i++)
    {
        if(arr[i]==1){k=0; continue;}
        if(k>0 && a[order[arr[i]-1]+k-1]!=a[order[arr[i]]+k-1]){k--; lcp[arr[i]]=k; continue;}
        for(j=k;j<=n;j++)
        {
            if(order[arr[i]-1]+j>n || order[arr[i]]+j>n || a[order[arr[i]-1]+j]!=a[order[arr[i]]+j]) break;
        }
        k=j;
        lcp[arr[i]]=k;
    }
}
void Manacher()
{
    int i,r=0,p=0;
    for(i=1;i<=n*2;i++)
    {
        if(r<i) d[i]=0;
        else d[i]=min(d[2*p-i],r-i);
        while(b[i+d[i]+1]==b[i-d[i]-1]) d[i]++;
        if(r<d[i]+i) r=d[i]+i, p=i;
    }
}
void solve()
{
    int i,big=0,pos,*q;
    for(i=1;i<=n*2;i++) arr2[(i-d[i])/2+1]=i;
    for(i=1;i<=n;i++)
    {
        if(big<arr2[i]) big=arr2[i];
        if(big%2==1) len[arr[i]]=((big/2+1)-i)*2+1;
        else len[arr[i]]=(big/2-i)*2+2;
    }
    st1[0]=-1;
    for(i=1;i<=n;i++)
    {
        while(st1[top]>=lcp[i]) top--;
        top++; st1[top]=lcp[i]; st2[top]=i;
        q=lower_bound(st1+1,st1+top+1,len[i]); pos=q-st1;
        p1[i]=st2[pos-1];
    }
    top=0;
    for(i=n;i>=1;i--)
    {
        while(st1[top]>=lcp[i+1]) top--;
        top++; st1[top]=lcp[i+1]; st2[top]=i;
        q=lower_bound(st1+1,st1+top+1,len[i]); pos=q-st1;
        p2[i]=st2[pos-1];
    }
    for(i=1;i<=n;i++)
    {
        if(dap<(long long)len[i]*(long long)(p2[i]-p1[i]+1)) dap=(long long)len[i]*(long long)(p2[i]-p1[i]+1);
    }
}
int main()
{
    int i;
    scanf("%s",a);
    n=strlen(a);
    for(i=n;i>=1;i--) a[i]=a[i-1]; a[0]=0;
    for(i=1;i<=n*2;i++){
        if(i%2==1) b[i]=a[i/2+1];
        else b[i]='#';
    }
    Suffix_Array();
    LCP();
    Manacher();
    solve();
    printf("%lld",dap);
    return 0;
}

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