4566. [HAOI2016]找相同字符【后缀自动机】

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #define N (400000+1000)
 5 using namespace std;
 6 
 7 char s[N],t[N];
 8 long long Ans;
 9 
10 struct SAM
11 {
12     int son[N][28],fa[N],step[N],right[N],wt[N],od[N];
13     int p,q,np,nq,last,cnt;
14     SAM(){last=++cnt;}
15     
16     void Insert(int x)
17     {
18         p=last; np=last=++cnt; step[np]=step[p]+1; right[np]=1;
19         while (!son[p][x] && p) son[p][x]=np,p=fa[p];
20         if (!p) fa[np]=1;
21         else
22         {
23             q=son[p][x];
24             if (step[p]+1==step[q]) fa[np]=q;
25             else
26             {
27                 nq=++cnt; step[nq]=step[p]+1;
28                 memcpy(son[nq],son[q],sizeof(son[q]));
29                 fa[nq]=fa[q]; fa[q]=fa[np]=nq;
30                 while (son[p][x]==q) son[p][x]=nq,p=fa[p];
31             }
32         }
33     }
34     void Init()
35     {
36         int len=strlen(s);
37         for (int i=1; i<=cnt; ++i) wt[step[i]]++;
38         for (int i=1; i<=len; ++i) wt[i]+=wt[i-1];
39         for (int i=cnt; i>=1; --i) od[wt[step[i]]--]=i;
40         for (int i=cnt; i>=1; --i) right[fa[od[i]]]+=right[od[i]];
41     }
42     void Solve(char s[])
43     {
44         int now=1,len=strlen(s),temp=0;
45         for (int i=0; i<len; ++i)
46         { 
47             while (now && !son[now][s[i]-‘a‘]) 
48                 now=fa[now],temp=step[now];
49             if (now==0){now=1; continue;}
50             now=son[now][s[i]-‘a‘],temp++;
51             Ans+=1ll*right[now]*(temp-step[fa[now]]);
52             int t=now;
53             while (fa[t]) t=fa[t],Ans+=1ll*right[t]*(step[t]-step[fa[t]]);
54         }
55     }
56 }SAM;
57 
58 int main()
59 {
60     scanf("%s%s",s,t);
61     int len=strlen(s);
62     for (int i=0; i<len; ++i)
63         SAM.Insert(s[i]-‘a‘);
64     SAM.Init(); 
65     SAM.Solve(t);
66     printf("%lld",Ans);
67 }