题目链接: https://www.lydsy.com/JudgeOnline/problem.php?id=4327

题解:

做法挺显然，建出AC自动机之后在上面跑，标记所有走过的点，然后再进行递推，如果\(fail[x]\)被标记则\(x\)被标记，然后每一个关键点往上找即可

有一个常数优化的技巧: 如果枚举每个\(x\)再vis[fail[x]]|=vis[x]的话好像还需要按深度排序，不如直接每到一个点直接不停地跳fail一路标记，直到遇到已标记点为止

代码

#include<cstdio>
#include<cstdlib>
#include<cstring>
using namespace std;const int N = 1e5;
const int LEN = 100;
const int M = 1e7;
const int SIZ = 1e7;
const int S = 4;
char b[N+3][LEN+3];
char a[M+3];
int len[N+3];
int son[SIZ+3][S+3];
int fail[SIZ+3];
int id[SIZ+3];
bool vis[SIZ+3];
int que[SIZ+3];
int ans[N+3];
int n,m,siz;int decode(char x)
{if(x=='E') return 1;else if(x=='S') return 2;else if(x=='W') return 3;else if(x=='N') return 4;
}void insertstr(int sid)
{int u = 0;for(int i=1; i<=len[sid]; i++){if(son[u][b[sid][i]]==0) {siz++; son[u][b[sid][i]] = siz;}u = son[u][b[sid][i]];}id[u] = sid;
}void buildACA()
{int head = 1,tail = 0;for(int i=1; i<=S; i++){if(son[0][i]) {tail++; que[tail] = son[0][i];} fail[son[0][i]] = 0;}while(head<=tail){int u = que[head]; head++;for(int i=1; i<=S; i++){if(son[u][i]) {fail[son[u][i]] = son[fail[u]][i]; tail++; que[tail] = son[u][i];}else {son[u][i] = son[fail[u]][i];}}}
}int main()
{scanf("%d%d",&m,&n);scanf("%s",a+1); for(int i=1; i<=m; i++) a[i] = decode(a[i]);for(int i=1; i<=n; i++){scanf("%s",b[i]+1); len[i] = strlen(b[i]+1);for(int j=1; j<=len[i]; j++) b[i][j] = decode(b[i][j]);insertstr(i);}buildACA();int u = 0; vis[0] = true;for(int i=1; i<=m; i++){vis[u] = true;u = son[u][a[i]];for(int j=u; vis[j]==false; j=fail[j]) {vis[j] = true;}}for(int i=1; i<=n; i++){u = 0;for(int j=1; j<=len[i]; j++){u = son[u][b[i][j]];if(!vis[u]) {break;}ans[i]++;}}for(int i=1; i<=n; i++) printf("%d\n",ans[i]);return 0;
}