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
}
else
j=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;
}
