wenbao与后缀自动机（SAM）

 1 作者：后缀自动机·张
 2 链接：https://zhuanlan.zhihu.com/p/25948077
 3 来源：知乎
 4 著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
 5 
 6 struct SAM{
 7     static const int maxn =  300010 * 2;
 8     struct node{
 9         node*nxt[26],*fail;
10         int len;
11     };
12     
13     node*root;int cnt;
14     node no[maxn];
15     node*newnode(){
16         return &no[cnt++];
17     }
18     SAM(){
19         cnt = 0;
20         root = newnode();
21     }
22     
23     node* add(node*p,int c){
24         node*cur = newnode();
25         cur->len = p->len+1;
26         while(p &&!p->nxt[c])p->nxt[c] = cur,p = p->fail;
27         if(!p){
28             cur->fail = root;return cur;
29         }
30         node*q = p->nxt[c];
31         if(q->len == p->len+1){
32             cur->fail = q;
33         }else{
34             node*nq = newnode();
35             *nq = *q;
36             nq->len = p->len+1;
37             q->fail = cur->fail = nq;
38             while(p&&p->nxt[c]==q)p->nxt[c] = nq,p = p->fail;
39         }
40         return cur;
41     }
42 
43     ll getNumOfDistinctSubstrings(){
44         auto ans = 0;
45         REP(i,1,cnt)ans+=no[i].len-no[i].fail->len;
46         return (ans);
47     }
48 };