题目链接：http://icpc.njust.edu.cn/Problem/Hdu/3695/
不加last指针的AC自动机会T，原因是他费了很多功夫在跳转上，而last指针是直接直到跳转的终止位置，直接跳转到终止位置上，所以只有一次跳转。未优化的fail指针最坏的情况下复杂度是O(|S|*|T|)，其中|S|是模式串长度的均值，|T|是文本串的 长度。
代码如下：
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define LL long long 4 #define ULL unsigned LL 5 #define fi first 6 #define se second 7 #define lson l,m,rt<<1 8 #define rson m+1,r,rt<<1|1 9 #define max3(a,b,c) max(a,max(b,c)) 10 #define min3(a,b,c) min(a,min(b,c)) 11 const int INF = 0x3f3f3f3f; 12 const LL mod = 1e9+7; 13 typedef pair<int,int> pll; 14 const int N = 1e6+10; 15 int tot = 2; 16 char str[N*26], tmp[N*26]; 17 int trie[N*4][26], cnt[N*26], fair[N*26]; 18 void init(){ 19 for(int i = 1; i < tot; i++){ 20 for(int j = 0; j < 26; j++) 21 trie[i][j] = 0; 22 } 23 tot = 2; 24 } 25 void Insert(){ 26 int rt = 1, len = strlen(str); 27 for(int i = 0; i < len; i++){ 28 int id = str[i] - 'A'; 29 if(!trie[rt][id]) { 30 cnt[tot] = 0; 31 fair[tot] = 0; 32 trie[rt][id] = tot++; 33 } 34 rt = trie[rt][id]; 35 } 36 cnt[rt]++; 37 } 38 void Build_tree(){ 39 queue<int> q; 40 q.push(1); 41 int p; 42 while(!q.empty()){ 43 int tmp = q.front(); 44 q.pop(); 45 for(int j = 0; j < 26; j++){ 46 if(trie[tmp][j]){ 47 if(tmp == 1) 48 fair[trie[tmp][j]] = 1; 49 else { 50 p = fair[tmp]; 51 while(p){ 52 if(trie[p][j]){ 53 fair[trie[tmp][j]] = trie[p][j]; 54 break; 55 } 56 else p = fair[p]; 57 } 58 if(!p) fair[trie[tmp][j]] = 1; 59 } 60 q.push(trie[tmp][j]); 61 } 62 } 63 } 64 } 65 int Find(int len){ 66 int ret = 0, rt = 1; 67 for(int i = 0; i < len; i++){ 68 int id = str[i] - 'A'; 69 while(rt != 1 && !trie[rt][id]) rt = fair[rt];; 70 if(trie[rt][id]) rt = trie[rt][id]; 71 int p = rt; 72 while(p != 1){ 73 if(cnt[p] >= 0){ 74 ret += cnt[p]; 75 cnt[p] = -1; 76 } 77 else break; 78 p = fair[p]; 79 } 80 } 81 rt = 1; 82 for(int i = len - 1; i >= 0; i--){ 83 int id = str[i] - 'A'; 84 while(rt != 1 && !trie[rt][id]) rt = fair[rt]; 85 if(trie[rt][id]) rt = trie[rt][id]; 86 int p = rt; 87 while(p != 1){ 88 if(cnt[p] >= 0){ 89 ret += cnt[p]; 90 cnt[p] = -1; 91 } 92 else break; 93 p = fair[p]; 94 } 95 } 96 return ret; 97 } 98 int main(){ 99 int t; 100 scanf("%d", &t); 101 while(t--){ 102 int n; 103 init(); 104 scanf("%d", &n); 105 while(n--){ 106 scanf("%s", str); 107 Insert(); 108 } 109 Build_tree(); 110 scanf("%s", tmp); 111 int len = strlen(tmp); 112 int ccc = 0; 113 for(int i = 0; i < len; i++){ 114 if(tmp[i] != '['){ 115 str[ccc++] = tmp[i]; 116 } 117 else { 118 int _c = 0; 119 i++; 120 while(isdigit(tmp[i])) 121 _c = _c *10 + (int)(tmp[i]-'0'), i++; 122 while(_c--) 123 str[ccc++] = tmp[i]; 124 i++; 125 } 126 } 127 printf("%d ", Find(ccc)); 128 } 129 return 0; 130 }