SPOJ LCS 后缀自动机找最大公共子串

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <iostream>
 4 #include <algorithm>
 5 using namespace std;
 6 #define M 26
 7 #define N 600000
 8 int cnt;
 9 char s1[N] , s2[N];
10 
11 struct SamNode{
12     SamNode *son[M] , *f;
13     int l;
14 }sam[N] , *root , *last;
15 
16 void init()
17 {
18     memset(sam , 0 , sizeof(sam));
19     root = last = &sam[cnt=0];
20 }
21 
22 void add(int x)
23 {
24     SamNode *p = &sam[++cnt] , *jp = last;
25     p->l = jp->l+1;
26     last = p;
27     for(; jp&&!jp->son[x] ; jp=jp->f) jp->son[x] = p;
28     if(!jp) p->f = root;
29     else{
30         if(jp->l+1 == jp->son[x]->l) p->f = jp->son[x];
31         else{
32             SamNode *r = &sam[++cnt] , *q = jp->son[x];
33             *r = *q;
34             r->l = jp->l+1; q->f = p->f = r;
35             for(; jp && jp->son[x]==q ; jp=jp->f) jp->son[x]=r;
36         }
37     }
38 }
39 
40 int solve(int len)
41 {
42     int ret = 0 , maxn=0;
43     SamNode *cur = root;
44     for(int i=0 ; i<len ; i++){
45         int x = s2[i]-‘a‘;
46         if(cur->son[x]){
47             ret++;
48             cur = cur->son[x];
49         }
50         else{
51             while(cur && !cur->son[x]) cur = cur->f;
52             if(!cur) cur = root , ret=0;
53             else{
54                 ret = cur->l+1;
55                 cur = cur->son[x];
56             }
57         }
58         maxn = max(maxn , ret);
59     }
60     return maxn;
61 }
62 
63 int main()
64 {
65    // freopen("in.txt" , "r" , stdin);
66    // freopen("out.txt" , "w" , stdout);
67     scanf("%s%s" , s1 , s2);
68     init();
69     int len1 = strlen(s1) , len2 = strlen(s2);
70     for(int i=0 ; i<len1 ; i++) add(s1[i]-‘a‘);
71     int ret = solve(len2);
72     printf("%d\n" , ret);
73     return 0;
74 }