POJ3415 Common Substrings

后缀数组 求长度不小于k的公共子串的个数

代码：

 #include <stdio.h>
 #include <string.h>

 const int maxn = ;
 int len, len1;
 int wa[maxn], wb[maxn], wv[maxn], wd[maxn], sa[maxn];
 int lcp[maxn], r[maxn], rank[maxn], height[maxn];

 int 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 n, int m){
     int i, j, p, *x=wa, *y=wb, *t;
     for(i = ; i < m; i++) wd[i] = ;
     for(i = ; i < n; i++) wd[x[i] = r[i]]++;
     for(i = ; i < m; i++) wd[i] += wd[i-];
     for(i = n-; i >= ; i--) sa[--wd[x[i]]] = i;
     for(j = , p = ; p < 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++) wd[i] = ;
         for(i = ; i < n; i++) wd[wv[i]]++;
         for(i = ; i < m; i++) wd[i] += wd[i-];
         for(i = n-; i >= ; i --) sa[--wd[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 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++);
     }
 }

 int main(){
     int k;
     char str1[maxn], str2[maxn];
     while(~scanf("%d", &k)){
         if(k==) break;
         scanf("%s%s",str1, str2);
         len1 = strlen(str1);
         len = strlen(str2);
         for(int i = ; i < len1; i++){
             r[i] = str1[i];
         }
         r[len1] = '$';
         for(int i = ; i < len; i++){
             r[i+len1+] = str2[i];
         }
         len += len1+;
         r[len] = ;
         da(r, len+, );
         calHeight(r, len);
         long long res = , sum;
         int head, tail;
         for(int i = ; i <= len; i++){
             if(height[i] < k){
                 sum = ;
                 head = tail = maxn;
             }
             else{
                 for(int j = head; j < tail; j++){
                     if(lcp[j] > height[i]){
                         sum -= lcp[j]-height[i];
                         lcp[j] = height[i];
                     }
                     else break;
                 }
                 if(sa[i-] > len1){
                     lcp[--head] = height[i];
                     sum += lcp[head]-k+;
                 }
                 if(sa[i] < len1) res += sum;
             }
         }
         for(int i = ; i <= len; i++){
             if(height[i] < k){
                 sum = ;
                 head = tail = maxn;
             }
             else{
                 for(int j = head; j < tail; j++){
                     if(lcp[j] > height[i]){
                         sum -= lcp[j]-height[i];
                         lcp[j] = height[i];
                     }
                     else break;
                 }
                 if(sa[i-] < len1){
                     lcp[--head] = height[i];
                     sum += lcp[head]-k+;
                 }
                 if(sa[i] > len1) res += sum;
             }
         }
         printf("%I64d\n", res);
     }
 }