zstu.4194: 字符串匹配(kmp)

4194: 字符串匹配

Time Limit: 1 Sec  Memory Limit: 128 MB Submit: 206  Solved: 78

Description

给你两个字符串A，B，请输出B字符串在A字符串中出现了几次。

Input

多组测试数据，每组输入两个字符串。字符串的长度 <= 1000000.

Output

输出B在A中出现的次数。

Sample Input

aaa aa

Sample Output

1

HINT

Source

WuYiqi

 1 #include <cstdio>
 2 #include <cstring>
 3
 4 const int N = 1000000 + 5;
 5 char s[N],t[N];
 6 int lens,lent;
 7
 8 int next[N];
 9
10 void get_fail() {
11     next[0] = -1;
12     for (int i = 1,j = -1; i < lent; ++ i) {
13         while (j != -1 && t[i] != t[j+1]) j = next[j];
14         next[i] = s[i] == t[j+1] ? ++ j : j;
15     }
16 }
17
18 int work() {
19     lens = strlen(s);
20     lent = strlen(t);
21     get_fail();
22     int ret = 0;
23     for (int i = 0,j = -1; i < lens; ++ i) {
24         while (j != -1 && s[i] != t[j+1]) j = next[j];
25         if (s[i] == t[j+1]) {
26             ++ j;
27             if (j == lent-1) {
28                 j = -1;
29                 ret ++;
30             }
31         }
32     }
33     return ret;
34 }
35
36 int main() {
37     while (scanf("%s",s) != EOF) {
38         scanf("%s",t);
39         printf("%d\n",work());
40     }
41     return 0;
42 }

纯粹的kmp（铭神写的，orz）