AC自动机+DP luoguP4052 and P3311
https://www.luogu.com.cn/problem/P4052
题意: 求长度为m的小写字母组成的字符串ss中包含给定字符串集合S中任意一个为子串的ss个数。
思路: 经典的在ac自动机上跑dp的套路,长度为m的不包含S中任意子串的字符串ss的个数等价于trie图上长度为m不经过有ed标记的节点以及有fail树上的父亲不含ed标记的节点(后者避免了串s不是字典串但s的后缀是字典串这种情况)
#include<bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(false) ,cin.tie(0), cout.tie(0);
//#pragma GCC optimize(3,"Ofast","inline")
#define ll long long
#define PII pair<int, int>
//#define int long long
const int N = 1e4 + 5;
const int M = 1e5 + 5;
const int INF = 0x3f3f3f3f;
const ll LNF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e4+7;
const double PI = acos(-1.0);
namespace AC {
int tr[N][26], tot;
bool e[N]; int fail[N];
void insert(char *s) {
int u = 0;
for ( int i = 1; s[i]; ++ i ) {
int ch = s[i] - 'A';
if(!tr[u][ch]) tr[u][ch] = ++ tot;
u = tr[u][ch];
}
e[u] = 1;
}
queue<int> q;
void build() {
for ( int i = 0; i < 26; ++ i ) {
if(tr[0][i]) q.push(tr[0][i]);
}
while(q.size()) {
int u = q.front();
q.pop();
for ( int i = 0; i < 26; ++ i ) {
if(tr[u][i]) {
fail[tr[u][i]] = tr[fail[u]][i];
e[tr[u][i]] |= e[tr[fail[u]][i]];
//避免了串s不是字典串但s的后缀是字典串这种情况
q.push(tr[u][i]);
} else {
tr[u][i] = tr[fail[u]][i];
}
}
}
}
}
char ss[105];
ll f[105][N];
int main() {
IOS
int n, m; cin >> n >> m;
for ( int i = 1; i <= n; ++ i ) {
cin >> (ss + 1);
AC::insert(ss);
}
AC::build();
f[0][0] = 1;
for ( int i = 1; i <= m; ++ i ) {
for ( int j = 0; j <= AC::tot; ++ j) {
for ( int k = 0; k < 26; ++ k ) {
if(!AC::e[AC::tr[j][k]]) {
(f[i][AC::tr[j][k]] += f[i - 1][j]) %= mod;
}
}
}
}
ll ans = 0;
for ( int i = 0; i <= AC::tot; ++ i) {
(ans += f[m][i]) %= mod;
}
ll res = 1;
for (int i = 1; i <= m; ++ i) res = res * 26 % mod;
cout << (res - ans + mod) % mod << '\n';
return 0;
}
https://www.luogu.com.cn/problem/P3311
AC自动机与数位dp结合
注意字典串含前导零,统计的串不能含前导0
那么 有前导0在自动机上就是从0点(字典树的根)开始匹配
#include<bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(false) ,cin.tie(0), cout.tie(0);
//#pragma GCC optimize(3,"Ofast","inline")
#define ll long long
#define PII pair<int, int>
//#define int long long
const int N = 1e4 + 5;
const int M = 1e5 + 5;
const int INF = 0x3f3f3f3f;
const ll LNF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double PI = acos(-1.0);
namespace AC {
int tr[N][10], tot;
bool e[N]; int fail[N];
void insert(char *s) {
int u = 0;
for ( int i = 1; s[i]; ++ i ) {
int ch = s[i] - '0';
if(!tr[u][ch]) tr[u][ch] = ++ tot;
u = tr[u][ch];
}
e[u] = 1;
}
queue<int> q;
void build() {
for ( int i = 0; i < 10; ++ i ) {
if(tr[0][i]) q.push(tr[0][i]);
}
while(q.size()) {
int u = q.front();
q.pop();
for ( int i = 0; i < 10; ++ i ) {
if(tr[u][i]) {
fail[tr[u][i]] = tr[fail[u]][i];
e[tr[u][i]] |= e[tr[fail[u]][i]];//
q.push(tr[u][i]);
} else {
tr[u][i] = tr[fail[u]][i];
}
}
}
}
}
ll f[1505][1505]; int num[1505];
int dfs(int pos, int tr_pos, bool limit, bool lead) {
if(!pos) return !lead;
if(!limit && !lead && f[pos][tr_pos] != - 1) return f[pos][tr_pos];
int len = limit ? num[pos] : 9;
int res = 0;
for ( int i = 0; i <= len; ++ i ) {
if(lead) {
if(!AC::e[AC::tr[0][i]]) {
res += dfs(pos - 1, AC::tr[0][i], limit && i == len, lead && !i);
res %= mod;
}
} else {
if(!AC::e[AC::tr[tr_pos][i]]) {
res += dfs(pos - 1, AC::tr[tr_pos][i], limit && i == len, lead && !i);
res %= mod;
}
}
}
if(!limit && !lead) f[pos][tr_pos] = res;
return res;
}
char ss[1505];
int cal(string ss) {
int n = ss.length();
reverse(ss.begin(), ss.end());
ss = " " + ss;
for ( int i = 1; i <= n; ++ i ) {
num[i] = ss[i] - '0';
}
return dfs(n, 0, 1, 1);
}
int main() {
IOS
string n;
int m; cin >> n >> m;
for ( int i = 1; i <= m; ++ i ) {
cin >> (ss + 1); AC::insert(ss);
}
AC::build();
memset(f, -1, sizeof f);
cout << cal(n) << '\n';
return 0;
}