【codevs3160】最长公共子串

 1 #include <cstdio>
 2 #include <cstring>
 3 #define N 200005
 4 int ws[N] , wv[N] , wa[N] , wb[N] , sa[N] , r[N] , rank[N] , height[N] , bl[N] , n , m = 28;
 5 char str[N];
 6 void da()
 7 {
 8     int i , j , p , *x = wa , *y = wb , *t;
 9     for(i = 0 ; i < m ; i ++ ) ws[i] = 0;
10     for(i = 0 ; i < n ; i ++ ) ws[x[i] = r[i]] ++ ;
11     for(i = 1 ; i < m ; i ++ ) ws[i] += ws[i - 1];
12     for(i = n - 1 ; i >= 0 ; i -- ) sa[--ws[x[i]]] = i;
13     for(p = j = 1 ; p < n ; j <<= 1 , m = p)
14     {
15         for(p = 0 , i = n - j ; i < n ; i ++ ) y[p ++ ] = i;
16         for(i = 0 ; i < n ; i ++ ) if(sa[i] - j >= 0) y[p ++ ] = sa[i] - j;
17         for(i = 0 ; i < n ; i ++ ) wv[i] = x[y[i]];
18         for(i = 0 ; i < m ; i ++ ) ws[i] = 0;
19         for(i = 0 ; i < n ; i ++ ) ws[wv[i]] ++ ;
20         for(i = 1 ; i < m ; i ++ ) ws[i] += ws[i - 1];
21         for(i = n - 1 ; i >= 0 ; i -- ) sa[--ws[wv[i]]] = y[i];
22         for(t = x , x = y , y = t , x[sa[0]] = 0 , p = i = 1 ; i < n ; i ++ )
23         {
24             if(y[sa[i - 1]] == y[sa[i]] && y[sa[i - 1] + j] == y[sa[i] + j])
25                 x[sa[i]] = p - 1;
26             else
27                 x[sa[i]] = p ++ ;
28         }
29     }
30     for(i = 1 ; i < n ; i ++ ) rank[sa[i]] = i;
31     for(p = i = 0 ; i < n - 1 ; height[rank[i ++ ]] = p)
32         for(p ? p -- : 0 , j = sa[rank[i] - 1] ; r[i + p] == r[j + p] ; p ++ );
33 }
34 bool judge(int mid)
35 {
36     int i;
37     for(i = 1 ; i < n - 1 ; i ++ )
38         if(height[i] >= mid && bl[sa[i]] != bl[sa[i - 1]])
39             return 1;
40     return 0;
41 }
42 int main()
43 {
44     int i , j , l , le , ri , mid , ans = 0;
45     for(i = 1 ; i <= 2 ; i ++ )
46     {
47         scanf("%s" , str);
48         l = strlen(str);
49         for(j = 0 ; j < l ; j ++ )
50         {
51             bl[n] = i;
52             r[n ++ ] = str[j] - ‘a‘ + 1;
53         }
54         r[n ++ ] = 27;
55     }
56     n ++ ;
57     da();
58     le = 0;
59     ri = n - 1;
60     while(le <= ri)
61     {
62         mid = (le + ri) >> 1;
63         if(judge(mid))
64         {
65             ans = mid;
66             le = mid + 1;
67         }
68         else ri = mid - 1;
69     }
70     printf("%d\n" , ans);
71     return 0;
72 }