BZOJ3238 [Ahoi2013]差异

首先把后缀数组和height数组都搞出来。。。

然后用两个单调栈维护$[l, r]$表示对于一个点$x$，满足$height[x] \le height[l..x] \ \&\&\  height[x] < height[x..r]$的最小的$l$和最大的$r$

这样子就可以保证不会重复计算了

 /**************************************************************
     Problem: 3238
     User: rausen
     Language: C++
     Result: Accepted
     Time:4496 ms
     Memory:20336 kb
 ****************************************************************/

 #include <cstdio>
 #include <cstring>

 using namespace std;
 typedef long long ll;
 const int N = 5e5 + ;

 int a[N], len;
 int sa[N], rank[N], height[N];

 inline void Sort(int *a, int *b, int *c, int n, int m) {
     static int i, sum[N];
     for (i = ; i <= m; ++i) sum[i] = ;
     for (i = ; i < n; ++i) ++sum[c[a[i]]];
     for (i = ; i <= m; ++i) sum[i] += sum[i - ];
     for (i = n - ; ~i; --i)
         b[--sum[c[a[i]]]] = a[i];
 }

 void make_sa(int *s) {
     int i, j;
     static int x[N], y[N];
     for (i = ; i < len; ++i) x[i] = s[i], rank[i] = i;
     Sort(rank, sa, x, len, );
     rank[sa[]] = ;
     for (i = ; i < len; ++i)
         rank[sa[i]] = rank[sa[i - ]] + (x[sa[i]] != x[sa[i - ]]);
     for (i = ; i <= len; i <<= ) {
         for (j = ; j < len; ++j)
             x[j] = rank[j], y[j] = j + i < len ? rank[j + i] : , sa[j] = j;
         Sort(sa, rank, y, len, len), Sort(rank, sa, x, len, len);
         rank[sa[]] = ;
         for (j = ; j < len; ++j)
             rank[sa[j]] = rank[sa[j - ]] + (x[sa[j]] != x[sa[j - ]] || y[sa[j]] != y[sa[j - ]]);
         if (rank[sa[len - ]] == len) return;
     }
 }

 void make_height() {
     int i, j;
     for (i = j = ; i < len; ++i) {
         if (j) --j;
         if (rank[i] != )
             while (a[i + j] == a[sa[rank[i] - ] + j]) ++j;
         height[rank[i]] = j;
     }
 }

 ll work() {
     int i;
     ll res;
     static int s[N], top, l[N], r[N];
     for (res = , i = ; i <= len; ++i) res += 1ll * i * (len - );
     for (s[top = ] = , i = ; i <= len; ++i) {
         while (height[i] <= height[s[top]] && top) --top;
         l[i] = s[top] + ;
         s[++top] = i;
     }
     for (s[top = ] = len + , i = len; i; --i) {
         while (height[i] < height[s[top]] && top) --top;
         r[i] = s[top] - ;
         s[++top] = i;
     }
     for (i = ; i <= len; ++i)
         res -= 2ll * (i - l[i] + ) * (r[i] - i + ) * height[i];
     return res;
 }

 int main() {
     int i;
     char ch;
     for (len = ; ;) {
         ch = getchar();
         if ('a' <= ch && ch <= 'z') a[len++] = ch - 'a' + ;
         else break;
     }
     make_sa(a);
     make_height();
     printf("%lld\n", work());
     return ;
 }