字符串hash

//#pragma comment(linker, "/STACK:102400000,102400000")
#include<cstdio>
#include<cstring>
#include<vector>
#include<queue>
#include<cmath>
#include<cctype>
#include<string>
#include<algorithm>
#include<iostream>
#include<ctime>
#include<map>
#include<set>
using namespace std;
#define MP(x,y) make_pair((x),(y))
#define PB(x) push_back(x)
typedef long long LL;
typedef unsigned long long ULL;
/* ****************** */
//const int INF=1000111222;
const double INFF=1e100;
const double eps=1e-8;
//const LL mod=1000000007;
const int mod=1000000007;
const int NN=100010;
const int MM=100010;
/* ****************** */

const ULL MOD=131;

ULL mul[NN];
ULL a[NN];
char ss[NN];

int main()
{
    int cas;
    int n,i,j,j1;
    ULL ans,t1,t2,t;

    mul[0]=1;
    for(i=1;i<NN;i++)
    {
        mul[i]=mul[i-1]*MOD;
    }

    scanf("%d",&cas);
    while(cas--)
    {
        scanf("%s",ss+1);
        n=strlen(ss+1);

        for(i=1;i<=n;i++)
        {
            a[i]=mul[i]*ss[i];
        }

        ans=0;
        for(i=2;i<n;i++)
        {
            j=i-1;
            j1=i+1;
            t1=t2=0;

            for(;j>=1 && j1<=n;j--,j1++)
            {
                if(ss[j]==ss[i] || ss[j1]==ss[i])
                    break;

                t1+=a[j];
                t2+=a[j1];
                if(t1*mul[i+1-j]==t2)
                {
                    t=j1-j+1;
                    ans+=t*t;
                }
            }
        }

        printf("%I64u\n",ans);
     //   cout<<ans<<endl;
    }
    return 0;
}

后缀数组

//#pragma comment(linker, "/STACK:102400000,102400000")
#include<cstdio>
#include<cstring>
#include<vector>
#include<queue>
#include<cmath>
#include<cctype>
#include<string>
#include<algorithm>
#include<iostream>
#include<ctime>
#include<map>
#include<set>
using namespace std;
#define MP(x,y) make_pair((x),(y))
#define PB(x) push_back(x)
typedef long long LL;
typedef unsigned long long ULL;
/* ****************** */
//const int INF=1000111222;
const double INFF=1e100;
const double eps=1e-8;
//const LL mod=1000000007;
const int mod=1000000007;
const int NN=100010;
const int MM=100010;
/* ****************** */

char ss[NN];
int a[NN];

//建立
int wa[NN],wb[NN],wv[NN],wss[NN],sa[NN];
//求高
int rank[NN],height[NN];
//RMQ
int rmq[NN][20],long2[NN];

int cmp(int *r,int a,int b,int l)
{return r[a]==r[b]&&r[a+l]==r[b+l];}
//r[n-1]==0;
void da(int *r,int n,int m)
{
    int i,j,p,*x=wa,*y=wb,*t;
    for(i=0;i<m;i++)wss[i]=0;
    for(i=0;i<n;i++)wss[x[i]=r[i]]++;
    for(i=1;i<m;i++)wss[i]+=wss[i-1];
    for(i=n-1;i>=0;i--)sa[--wss[x[i]]]=i;
    for(j=1,p=1;p<n;j*=2,m=p)
    {
        for(p=0,i=n-j;i<n;i++)y[p++]=i;
        for(i=0;i<n;i++)if(sa[i]>=j)y[p++]=sa[i]-j;

        for(i=0;i<n;i++)wv[i]=x[y[i]];
        for(i=0;i<m;i++)wss[i]=0;
        for(i=0;i<n;i++)wss[wv[i]]++;
        for(i=1;i<m;i++)wss[i]+=wss[i-1];
        for(i=n-1;i>=0;i--)sa[--wss[wv[i]]]=y[i];

        for(t=x,x=y,y=t,p=1,x[sa[0]]=0,i=1;i<n;i++)
            x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;
    }
    return;
}

void calheight(int *r,int n)
{
    int i,j,k=0;
    for(i=1;i<=n;i++)rank[sa[i]]=i;
    for(i=0;i<n;height[rank[i++]]=k)
        for(k?k--:0,j=sa[rank[i]-1];r[i+k]==r[j+k];k++);
    return;
}

void initRMQ(int n)
{
    int i,j,en;
    long2[1]=0;
    for(i=2;i<=n;i++)
    {
        long2[i]=long2[i-1]+(i==(i&(-i)));
    }
    for(i=1;i<=n;i++)rmq[i][0]=height[i];
    for(j=1;j<=long2[n];j++)
    {
        en=n+1-(1<<j);
        for(i=1;i<=en;i++)
            rmq[i][j]=min(rmq[i][j-1],rmq[ i+(1<<(j-1)) ][j-1]);
    }
}
int ask_lcp(int i,int j)
{
    i=rank[i],j=rank[j];
    if(i>j)swap(i,j);
    i++;
    int k=long2[j-i+1];
    int ans=min(rmq[i][k],rmq[ j+1-(1<<k) ][k]);
    return ans;
}

int main()
{
    int cas;
    int n,i,j,j1,lcp;
    ULL ans,t;
    scanf("%d",&cas);
    while(cas--)
    {
        scanf("%s",ss);
        n=strlen(ss);
        for(i=0;i<n;i++)
        {
            a[i]=ss[i]-'a'+1;
        }
        a[n]=0;
        da(a,n+1,30);
        calheight(a,n);
        initRMQ(n);
        
        ans=0;
        for(i=1;i<n;i++)
        {
            j=i-1;
            j1=i+1;

            for(;j>=0 && j1<n;j--,j1++)
            {
                if(ss[j]==ss[i] || ss[j1]==ss[i])
                    break;

                lcp=ask_lcp(j,i+1);

                if(lcp>=i-j)
                {
                    t=j1-j+1;
                    ans+=t*t;
                }
            }
        }
        printf("%I64u\n",ans);
     //   cout<<ans<<endl;
    }
    return 0;
}