POJ 2774 - Long Long Message

求两串的最长相同公共连续子串

将两串拼接在一起，中间用一个未出现过的符号隔开

求 sa, height

sa[i] 与 sa[i-1] 不在同一个串时的 height[i] 的最大值就是答案

 

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 const int MAXN = 200005;
 6 
 7 struct SuffixArray
 8 {
 9     int wa[MAXN], wb[MAXN], wsf[MAXN], wv[MAXN];
10     int Cmp(int r[], int a, int b, int k)
11     {
12         return r[a] == r[b] && r[a+k] == r[b+k];
13     }
14     void GetSa(int r[], int sa[], int n, int m)
15     {
16         int i, j, p, *x = wa, *y = wb, *t;
17         for (i = 0; i < m; i++) wsf[i] = 0;
18         for (i = 0; i < n; i++) wsf[x[i]=r[i]]++;
19         for (i = 1; i < m; i++) wsf[i] += wsf[i-1];
20         for (i = n - 1; i >= 0; i--) sa[--wsf[x[i]]] = i;
21         for (p = j = 1; p < n; j *= 2, m = p)
22         {
23             for (p = 0, i = n - j; i < n; i++) y[p++] = i;
24             for (i = 0; i < n; i++) if(sa[i] >= j) y[p++] = sa[i] - j;
25             for (i = 0; i < n; i++) wv[i] = x[y[i]];
26             for (i = 0; i < m; i++) wsf[i] = 0;
27             for (i = 0; i < n; i++) wsf[wv[i]]++;
28             for (i = 1; i < m; i++) wsf[i] += wsf[i-1];
29             for (i = n-1; i >= 0; i--) sa[--wsf[wv[i]]] = y[i];
30             swap(x, y);
31             x[sa[0]] = 0;
32             for (p = i = 1; i < n; i++)
33                 x[sa[i]] = Cmp(y, sa[i-1], sa[i], j) ? p - 1: p++;
34         }
35     }
36     void GetHeight(int r[], int sa[], int rnk[], int height[], int n)
37     {
38         int i, j, k = 0;
39         for (i = 1; i <= n; i++)
40             rnk[sa[i]] = i;
41         for (i = 0; i < n; i++)
42         {
43             if (k) k--;
44             j = sa[rnk[i]-1];
45             while (r[i+k] == r[j+k]) k++;
46             height[rnk[i]] = k;
47         }
48     }
49     
50 }suffixArray;
51 int r[MAXN], sa[MAXN], rnk[MAXN], height[MAXN];
52 char s[MAXN];
53 int len1, len2;
54 bool check(int i, int j)
55 {
56     return ( sa[i] < len1 && sa[j] > len1 ) ||
57            ( sa[i] > len1 && sa[j] < len1 ) ;
58 }
59 int main()
60 {
61     scanf("%s",s);
62     len1 = strlen(s);
63     s[len1] = '#';
64     scanf("%s", s + len1 + 1);
65     len2 = strlen(s);
66     int m = 0;
67     for (int i = 0; i < len2; i++)
68     {
69         if(i == len1) r[i] = 1;
70         else r[i] = s[i] - 'a' + 2;
71         m = max(r[i] + 1, m);
72     }
73     r[len2] = 0;
74     suffixArray.GetSa(r, sa, len2 + 1, m);
75     suffixArray.GetHeight(r, sa, rnk, height, len2);
76     int ans = 0;
77     for (int i = 1; i < len2; i++)
78     {
79         if(check(i,i-1))
80         {
81             ans = max(height[i], ans);
82         }
83     }
84     printf("%d\n", ans);
85 }

 

posted @ 2016-08-08 19:34  nicetomeetu  阅读(127)  评论(0)  编辑  收藏  举报