POJ3693 Maximum repetition substring

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<cstdio>
 6 using namespace std;
 7 const int N=2e6+10;
 8 int wv[N],wu[N],wa[N],wb[N],sa[N],rank[N],height[N],r[N],f[N][25];
 9 int cmp(int *r,int a,int b,int l)
10 {
11     return r[a]==r[b]&&r[a+l]==r[b+l];
12 }
13 
14 void da(int *r,int *sa,int n,int m)
15 {
16     int i,j,p;int *x=wa,*y=wb;
17     for(i=0;i<m;++i)wu[i]=0;
18     for(i=0;i<n;++i)wu[x[i]=r[i]]++;
19     for(i=1;i<m;++i)wu[i]+=wu[i-1];
20     for(i=n-1;i>=0;--i)sa[--wu[x[i]]]=i;
21     
22     for(j=1,p=1;p<n;j<<=1,m=p)
23     {
24         for(p=0,i=n-j;i<n;++i)y[p++]=i;
25         for(i=0;i<n;++i)if(sa[i]>=j)y[p++]=sa[i]-j;
26         for(i=0;i<n;++i)wv[i]=x[y[i]];
27         for(i=0;i<m;++i)wu[i]=0;
28         for(i=0;i<n;++i)wu[wv[i]]++;
29         for(i=1;i<m;++i)wu[i]+=wu[i-1];
30         for(i=n-1;i>=0;--i)sa[--wu[wv[i]]]=y[i];
31         for(swap(x,y),p=1,x[sa[0]]=0,i=1;i<n;++i)
32         x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;
33     }
34     return;
35 }
36 void calcHeight(int *rank,int *sa,int n)
37 {
38     int i,j,k=0;
39     for(i=1;i<=n;++i)rank[sa[i]]=i;
40     for(i=0;i<n;height[rank[i++]]=k)
41         for(k?k--:0,j=sa[rank[i]-1];r[i+k]==r[j+k];++k);
42     return;
43 }
44 void makest(int n)
45 {
46     for(int i=1;i<=n;++i)f[i][0]=height[i];
47     for(int j=1;j<=20;++j)
48     for(int i=1;i+(1<<j)-1<=n;++i)
49     f[i][j]=min(f[i][j-1],f[i+(1<<j-1)][j-1]); 
50 }
51 int query(int x,int y)
52 {
53     if(x>y)swap(x,y);
54     x++;int k=0;
55     while(x+(1<<(k+1))<=y)++k;
56     return min(f[x][k],f[y-(1<<k)+1][k]);
57 }
58 int T;char s[N];
59 int main()
60 {
61     while(~scanf("%s",s+1))
62     {
63         int n=strlen(s+1);T++;
64         if(n==1&&s[1]==‘#‘)return 0;
65         printf("Case %d: ",T);
66         for(int i=1;i<=n;++i)r[i-1]=s[i];r[n]=0;
67         da(r,sa,n+1,246);
68         calcHeight(rank,sa,n);
69         makest(n);int ans=0,al=0,ar=0;
70         for(int l=1;l*2<=n;++l)
71         {
72             for(int i=0;l*(i+1)+1<=n;++i)
73             {
74                 int x=l*i+1,y=l*(i+1)+1;
75                 if(s[x]!=s[y])continue;
76                 int z=query(rank[x-1],rank[y-1]);
77                 int rr=y+z-1,ll=0;
78                 for(int j=0;j<l;++j)
79                 {
80                     if(x-j<1||s[x-j]!=s[y-j])break;
81                     ll=x-j;int tmp=(rr-ll+1)/l;
82                     if(tmp>ans||(tmp==ans&&rank[ll-1]<rank[al-1]))
83                     {
84                         ans=tmp;al=ll;ar=ll+l*tmp-1;
85                     }
86                 }
87             }
88         }
89         if(!ans)printf("%c",s[sa[1]+1]);
90         else for(int i=al;i<=ar;++i)printf("%c",s[i]);
91         puts("");
92     }
93     return 0;
94 }