HDU 4622 Reincarnation (后缀自动机）

Now you are back,and have a task to do:
Given you a string s consist of lower-case English letters only,denote f(s) as the number of distinct sub-string of s.
And you have some query,each time you should calculate f(s[l...r]), s[l...r] means the sub-string of s start from l end at r.

InputThe first line contains integer T(1<=T<=5), denote the number of the test cases.
For each test cases,the first line contains a string s(1 <= length of s <= 2000).
Denote the length of s by n.
The second line contains an integer Q(1 <= Q <= 10000),denote the number of queries.
Then Q lines follows,each lines contains two integer l, r(1 <= l <= r <= n), denote a query.OutputFor each test cases,for each query,print the answer in one line.Sample Input

2
bbaba
5
3 4
2 2
2 5
2 4
1 4
baaba
5
3 3
3 4
1 4
3 5
5 5

Sample Output

3
1
7
5
8
1
3
8
5
1

题意是求[l,r]的区间里有多少个子串，因为字符串的长度范围很小，我们可以将每个后缀分别放入自动机中预处理。
然后节点p的贡献就是p->step-p->link->step;
就能算出当前子串的贡献
代码如下：

#include <iostream>
#include <string.h>
#include <algorithm>
#include <stdio.h>

using namespace std;
const int N=2200;
typedef long long ll;
ll num;
ll ans[N][N];
char A[N];
struct State
{
    State *link,*go[26];
    int step;
    int maxx;
    void clear()
    {
        maxx=0;
        link=0;
        step=0;
        memset(go,0,sizeof(go));
    }
    int gx()
    {
      if(link==NULL)return 0;
      return step-link->step;
    }
}*root,*last;
int cnt[N];
int lenA;
State statePool[N*2],*b[N*2],*cur;

void init()
{
    cur=statePool;
    root=last=cur++;
    root->clear();
}

void Insert(int w)
{
    State *p=last;
    State *np=cur++;
    np->clear();
    np->step=p->step+1;
    while(p&&!p->go[w])
        p->go[w]=np,p=p->link;
    if(p==0){
        np->link=root;
        num+=np->gx();
    }
    else
    {
        State *q=p->go[w];
        if(p->step+1==q->step){
            np->link=q;
            num+=np->gx();
        }
        else
        {
            State *nq=cur++;
            nq->clear();
            memcpy(nq->go,q->go,sizeof(q->go));
            num-=q->gx();
            nq->step=p->step+1;
            nq->link=q->link;
            q->link=nq;
            np->link=nq;
            num+=q->gx()+nq->gx()+np->gx();
            while(p&&p->go[w]==q)
                p->go[w]=nq, p=p->link;
        }
    }
    last=np;
}
void solve()
{
   for(int i=0;i<lenA;i++)
   {
       num=0;
       init();
       for(int j=i;j<lenA;j++)
       {
          Insert(A[j]-'a');
          ans[i][j]=num;
       }
   }
}
int main()
{
    int t,q,l,r;
    scanf("%d",&t);
    while(t--)
    {
        memset(ans,0,sizeof(ans));
      scanf("%s",A);
      lenA=strlen(A);
      solve();
      scanf("%d",&q);
      while(q--)
      {
          scanf("%d%d",&l,&r);
          printf("%lld
",ans[l-1][r-1]);
      }
     }
    return 0;
}