【转】HDU 6194 string string string （2017沈阳网赛-后缀数组）

  1 #include <cstdio>
  2 #include <cstring>
  3 #include <algorithm>
  4 using namespace std;
  5 
  6 const int maxn = 100000 + 10;
  7 
  8 int t1[maxn], t2[maxn], c[maxn];
  9 
 10 bool cmp(int* r, int a,int b,int l){
 11     return r[a] == r[b] && r[a+l] == r[b+l];
 12 }
 13 
 14 void da(int str[], int sa[], int Rank[], int lcp[], int n, int m){
 15     ++n;
 16     int i, j, p, *x = t1, *y = t2;
 17     for (i = 0; i < m; ++i) c[i] = 0;
 18 //        puts("hha");
 19     for (i = 0; i < n; ++i) c[x[i] = str[i] ]++;
 20     for (i = 1; i < m; ++i) c[i] += c[i-1];
 21     for (i = n-1; i >= 0; --i) sa[--c[x[i] ] ] = i;
 22     for (j = 1; j <= n; j <<= 1){
 23         p = 0;
 24         for (i = n-j; i < n; ++i) y[p++] = i;
 25         for (i = 0; i < n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;
 26         for (i = 0; i < m; ++i) c[i] = 0;
 27         for (i = 0; i < n; ++i) c[x[y[i] ] ]++;
 28 
 29         for (i = 1; i < m; ++i) c[i] += c[i-1];
 30         for (i = n-1; i >= 0; --i) sa[--c[x[y[i] ] ] ] = y[i];
 31 
 32         swap(x,y);
 33         p = 1; x[sa[0] ] = 0;
 34         for (i = 1; i < n; ++i){
 35             x[sa[i] ] = cmp(y, sa[i-1], sa[i], j) ? p-1 : p++;
 36 
 37 
 38         }
 39 
 40         if (p >= n)break;
 41         m= p;
 42 
 43 
 44     }
 45 
 46     int k = 0;
 47     n--;
 48     for (i = 0; i <= n; ++i) Rank[sa[i] ] = i;
 49     for (i = 0; i < n; ++i){
 50         if (k)--k;
 51         j = sa[Rank[i]-1 ];
 52         while(str[i+k] == str[j+k])++k;
 53         lcp[Rank[i] ] = k;
 54     }
 55 }
 56 
 57 int lcp[maxn], a[maxn], sa[maxn], Rank[maxn];
 58 
 59 char s[maxn];
 60 
 61 int d[maxn][40];
 62 int len;
 63 
 64 void rmq_init(int* A, int n){
 65     for (int i = 0; i < n; ++i) d[i][0] = A[i];
 66     for (int j = 1; (1<<j) <= n; ++j)
 67         for (int i = 0; i + (1<<j) - 1 < n ; ++i)
 68             d[i][j] = min(d[i][j-1], d[i + (1<< (j-1))][j-1]);
 69 }
 70 
 71 int ASK(int l,int r){
 72     int k = 0;
 73     while((1<<(k+1)) <= r-l + 1)++k;
 74     return min(d[l][k], d[r-(1<<k) + 1][k]);
 75 }
 76 
 77 int ask(int l,int r){
 78     if (l == r) return len - sa[r]; /// l == r的话 是一个串， 返回本身的长度即可。
 79     return ASK(l + 1, r); ///否则在rmq查询。
 80 }
 81 
 82 //
 83 int main(){
 84     int T;
 85     scanf("%d", &T);
 86 
 87     while(T--){
 88         int k;
 89         scanf("%d", &k);
 90         scanf("%s", s);
 91         len = strlen(s);
 92         for (int i = 0; i < len; ++i){
 93             a[i] = s[i] - ‘a‘ + 1;
 94         }
 95         a[len] = 0;
 96         da(a, sa, Rank, lcp, len, 30);
 97         rmq_init(lcp, len + 1);
 98         long long ans = 0;
 99         for (int i = 1; i + k - 1 <= len; ++i){
100             ans += ask(i, i + k - 1);
101             if (i - 1 > 0)ans -= ask(i - 1, i + k - 1); ///注意边界问题。
102             if (i + k <= len)ans -= ask(i, i + k);
103             if (i - 1 > 0 && i + k <= len)ans += ask(i - 1 , i + k);
104         }
105         printf("%I64d\n", ans);
106 
107 
108     }
109     return 0;
110 }
111