[JZOJ 5129] 字符串

题意：统计本质不同的串的个数。

思路：

显然后缀自动机，对于每个串建一个\(SAM\)统计即可。

#include <bits/stdc++.h>
using namespace std;
int root;
int lst;
int tot;
const int maxn = 2000010;
const int mod = 1e9+7;
int son[maxn][26];
int fa[maxn];
int d[maxn];
int f[maxn];
inline void upd(int &x,int y) {
	x += y;
	if(x >= mod) x -= mod;
}
inline void extend(int c) {
	int np = ++tot;
	int p = lst;
	d[np] = d[p] + 1;
	lst = np;
	for(;p && !son[p][c];son[p][c] = np,p = fa[p]);
	if(!p) {
		fa[np] = root;
	}
	else {
		int q = son[p][c];
		if(d[q] == d[p] + 1) {
			fa[np] = q;
		}
		else {
			int nq = ++tot;
			d[nq] = d[p] + 1;
			for(int i = 0;i < 26; ++i) {
				son[nq][i] = son[q][i];
			}
			fa[nq] = fa[q];
			fa[q] = fa[np] = nq;
			for(;p && son[p][c] == q;son[p][c] = nq,p = fa[p]);
		}
	}
}
int r[maxn];
int pos[maxn];
int Order[maxn];
int n;
inline bool cmp(int a,int b) {
	return pos[a] == pos[b] ? d[a] < d[b] : pos[a] < pos[b];
}
int main () {
	freopen("str.in","r",stdin);
	freopen("str.out","w",stdout);
	scanf("%d",&n);
	for(int i = 1;i <= n; ++i) {
		char s[maxn];
		scanf("%s",s);
		int len = strlen(s);
		root = ++tot;
		lst = root;
		r[i] = lst;
		for(int j = 0;j < len; ++j) {
			extend(s[j] - 'a');
		}
		for(int j = r[i];j <= tot; ++j) {
			pos[j] = i;
		}
	}
	r[n + 1] = tot + 1;
	for(int i = n;i >= 1; --i) {
		for(int j = r[i];j < r[i + 1]; ++j) {
			for(int k = 0;k < 26; ++k) {
				if(!son[j][k]) {
					son[j][k] = son[r[i + 1]][k];
				}
			}
		}
	}
	for(int i = 1;i <= tot; ++i) {
		Order[i] = i;
	}
	sort(Order+1,Order+tot+1,cmp);
	for(int i = tot;i; --i) {
		int tmp = Order[i];
		f[tmp] = 1;
		for(int j = 0;j < 26; ++j) {
			upd(f[tmp],f[son[tmp][j]]);
		}
	}
	printf("%d\n",f[1]);
	return 0;
}