A - Oulipo（KMP算法经典）

详细ＫＭＰ见http://blog.csdn.net/u014665013/article/details/37995355

Description

The French author Georges Perec (1936–1982) once wrote a book, La disparition, without the letter'e'. He was a member of the Oulipo group. A quote from the book:

Tout avait Pair normal, mais tout s’affirmait faux. Tout avait Fair normal, d’abord, puis surgissait l’inhumain, l’affolant. Il aurait voulu savoir où s’articulait l’association qui l’unissait au roman : stir son tapis, assaillant à tout instant son imagination, l’intuition d’un tabou, la vision d’un mal obscur, d’un quoi vacant, d’un non-dit : la vision, l’avision d’un oubli commandant tout, où s’abolissait la raison : tout avait l’air normal mais…

Perec would probably have scored high (or rather, low) in the following contest. People are asked to write a perhaps even meaningful text on some subject with as few occurrences of a given “word” as possible. Our task is to provide the jury with a program that counts these occurrences, in order to obtain a ranking of the competitors. These competitors often write very long texts with nonsense meaning; a sequence of 500,000 consecutive'T's is not unusual. And they never use spaces.

So we want to quickly find out how often a word, i.e., a given string, occurs in a text. More formally: given the alphabet {'A','B','C', …, 'Z'} and two finite strings over that alphabet, a wordW and a textT, count the number of occurrences of W inT. All the consecutive characters of W must exactly match consecutive characters ofT. Occurrences may overlap.

Input

The first line of the input file contains a single number: the number of test cases to follow. Each test case has the following format:

One line with the word W, a string over {'A', 'B','C', …,'Z'}, with 1 ≤ |W| ≤ 10,000 (here |W| denotes the length of the stringW).
One line with the text T, a string over {'A', 'B','C', …,'Z'}, with |W| ≤ |T| ≤ 1,000,000.

Output

For every test case in the input file, the output should contain a single number, on a single line: the number of occurrences of the wordW in the textT.

Sample Input

3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

Sample Output

1
3
0

题意：

找出在目标串中有多少模式串（相邻两串中可以重叠）

代码

#include <stdio.h>
#include <string.h>
int next[10005];
char str1[1000005],str2[10005];
void getnext(int len)//此处也可以将int next[]改写成  int* next[]
{int j,k;j=0; k=-1; next[0]=-1;while(j<len){if(k==-1 ||str2[j]==str2[k]){j++;k++;next[j]=k;}else k=next[k];}
}
int kmp(int len1,int len2)//kmp算法
{int count=0;int i=0,j=0;getnext(len2);while(i<len1){if(j==-1||str1[i]==str2[j]){++i;++j;   //j控制子串回溯和遍历 }elsej=next[j];if(j == len2){count++;j = next[j];   //当有一个匹配成功的时候，相当于匹配失败，重新定位子串的匹配位置 }}return  count;
}
int main()
{int Case;int len1,len2;scanf("%d",&Case);getchar();//注意吸收空格 while(Case--){gets(str2);gets(str1);len1 = strlen(str1), len2 = strlen(str2);printf("%d\n",kmp(len1,len2));}return 0;
}

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