【HDOJ】1403 Longest Common Substring

后缀数组2倍增可解。

 #include <cstdio>
 #include <cstring>
 #include <cstdlib>

 #define MAXM 28
 #define MAXN 100010

 int wa[MAXN*];
 int wb[MAXN*];
 int wv[MAXN*];
 int ws[MAXN*];
 char s[MAXN];
 int str[MAXN*], sa[MAXN*];
 int height[MAXN*], rank[MAXN*];

 bool cmp(int *r, int a, int b, int l) {
     return r[a]==r[b] && r[a+l]==r[b+l];
 }

 void da(int *r, int *sa, int n, int m) {
     int i, j, *x = wa, *y = wb, *t;
     int p;

     for (i=; i<m; ++i) ws[i] = ;
     for (i=; i<n; ++i) ws[x[i]=r[i]]++;
     for (i=; i<m; ++i) ws[i] += ws[i-];
     for (i=n-; i>=; --i) sa[--ws[x[i]]] = i;
     for (j=, p=; j<n; j*=, m=p) {
         for (p=, i=n-j; i<n; ++i) y[p++] = i;
         for (i=; i<n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;
         for (i=; i<n; ++i) wv[i] = x[y[i]];
         for (i=; i<m; ++i) ws[i] = ;
         for (i=; i<n; ++i) ws[wv[i]]++;
         for (i=; i<m; ++i) ws[i] += ws[i-];
         for (i=n-; i>=; --i) sa[--ws[wv[i]]] = y[i];
         for (t=x, x=y, y=t, p=, x[sa[]]=, i=; i<n; ++i)
             x[sa[i]] = cmp(y, sa[i-], sa[i], j) ? p-:p++;
     }
 }

 void calheight(int *r, int *sa, int n) {
     int i, j, k=;

     for (i=; i<=n; ++i) rank[sa[i]] = i;
     for (i=; i<n; height[rank[i++]]=k)
         for (k?k--:, j=sa[rank[i]-]; r[i+k]==r[j+k]; ++k)
             /*do nothing*/;
 }

 void printRank(int n) {
     int i;

     printf("\nprint rank...\n");
     for (i=; i<n; ++i)
         printf("%d ", rank[i]);
     printf("\n");
 }

 void printSa(int n) {
     int i;

     printf("\nprint sa...\n");
     for (i=; i<n; ++i)
         printf("%d ", sa[i]);
     printf("\n");
 }

 void printHeight(int n) {
     int i;

     printf("\nprint height...\n");
     for (i=; i<n; ++i)
         printf("%d ", height[i]);
     printf("\n");
 }

 int main() {
     int l1, l2, l;
     int i, j, k;
     int ans;

 #ifndef ONLINE_JUDGE
     freopen("data.in", "r", stdin);
 #endif

     while (scanf("%s", s) != EOF) {
         l = ;
         for (l1=; s[l1]; l1++)
             str[l++] = s[l1] - 'a' + ;
         str[l++] = ;    // split two strings
         scanf("%s", s);
         for (l2=; s[l2]; l2++)
             str[l++] = s[l2] - 'a' + ;
         str[l] = ;
         da(str, sa, l+, MAXM);
         calheight(str, sa, l);
     #ifndef ONLINE_JUDGE
         printRank(l+);
         printSa(l+);
         printHeight(l);
     #endif
         ans = -;
         for (i=; i<=l; ++i) {
             if (height[i] > ans) {
                 if ((sa[i-]<l1 && sa[i]>l1) || (sa[i-]>l1 && sa[i]<l1))
                     ans = height[i];
             }
         }
         printf("%d\n", ans);
     }

     return ;
 }