【HDOJ】1403 Longest Common Substring

后缀数组2倍增可解。

  1 #include <cstdio>
  2 #include <cstring>
  3 #include <cstdlib>
  4 
  5 #define MAXM 28
  6 #define MAXN 100010
  7 
  8 int wa[MAXN*2];
  9 int wb[MAXN*2];
 10 int wv[MAXN*2];
 11 int ws[MAXN*2];
 12 char s[MAXN];
 13 int str[MAXN*2], sa[MAXN*2];
 14 int height[MAXN*2], rank[MAXN*2];
 15 
 16 bool cmp(int *r, int a, int b, int l) {
 17     return r[a]==r[b] && r[a+l]==r[b+l];
 18 }
 19 
 20 void da(int *r, int *sa, int n, int m) {
 21     int i, j, *x = wa, *y = wb, *t;
 22     int p;
 23     
 24     for (i=0; i<m; ++i) ws[i] = 0;
 25     for (i=0; i<n; ++i) ws[x[i]=r[i]]++;
 26     for (i=1; i<m; ++i) ws[i] += ws[i-1];
 27     for (i=n-1; i>=0; --i) sa[--ws[x[i]]] = i;
 28     for (j=1, p=1; j<n; j*=2, m=p) {
 29         for (p=0, i=n-j; i<n; ++i) y[p++] = i;
 30         for (i=0; i<n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;
 31         for (i=0; i<n; ++i) wv[i] = x[y[i]];
 32         for (i=0; i<m; ++i) ws[i] = 0;
 33         for (i=0; i<n; ++i) ws[wv[i]]++;
 34         for (i=1; i<m; ++i) ws[i] += ws[i-1];
 35         for (i=n-1; i>=0; --i) sa[--ws[wv[i]]] = y[i];
 36         for (t=x, x=y, y=t, p=1, x[sa[0]]=0, i=1; i<n; ++i)
 37             x[sa[i]] = cmp(y, sa[i-1], sa[i], j) ? p-1:p++;
 38     }
 39 }
 40 
 41 void calheight(int *r, int *sa, int n) {
 42     int i, j, k=0;
 43     
 44     for (i=1; i<=n; ++i) rank[sa[i]] = i;
 45     for (i=0; i<n; height[rank[i++]]=k)
 46         for (k?k--:0, j=sa[rank[i]-1]; r[i+k]==r[j+k]; ++k)
 47             /*do nothing*/;
 48 }
 49 
 50 void printRank(int n) {
 51     int i;
 52     
 53     printf("\nprint rank...\n");
 54     for (i=0; i<n; ++i)
 55         printf("%d ", rank[i]);
 56     printf("\n");
 57 }
 58 
 59 void printSa(int n) {
 60     int i;
 61     
 62     printf("\nprint sa...\n");
 63     for (i=0; i<n; ++i)
 64         printf("%d ", sa[i]);
 65     printf("\n");
 66 }
 67 
 68 void printHeight(int n) {
 69     int i;
 70     
 71     printf("\nprint height...\n");
 72     for (i=0; i<n; ++i)
 73         printf("%d ", height[i]);
 74     printf("\n");
 75 }
 76 
 77 int main() {
 78     int l1, l2, l;
 79     int i, j, k;
 80     int ans;
 81     
 82 #ifndef ONLINE_JUDGE
 83     freopen("data.in", "r", stdin);
 84 #endif
 85 
 86     while (scanf("%s", s) != EOF) {
 87         l = 0;
 88         for (l1=0; s[l1]; l1++)
 89             str[l++] = s[l1] - 'a' + 2;
 90         str[l++] = 1;    // split two strings
 91         scanf("%s", s);
 92         for (l2=0; s[l2]; l2++)
 93             str[l++] = s[l2] - 'a' + 2;
 94         str[l] = 0;
 95         da(str, sa, l+1, MAXM);
 96         calheight(str, sa, l);
 97     #ifndef ONLINE_JUDGE
 98         printRank(l+1);
 99         printSa(l+1);
100         printHeight(l);
101     #endif
102         ans = -1;
103         for (i=2; i<=l; ++i) {
104             if (height[i] > ans) {
105                 if ((sa[i-1]<l1 && sa[i]>l1) || (sa[i-1]>l1 && sa[i]<l1))
106                     ans = height[i];
107             }
108         }
109         printf("%d\n", ans);
110     }
111 
112 
113     return 0;
114 }

 

posted on 2014-12-19 10:22  Bombe  阅读(177)  评论(0)  编辑  收藏  举报

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