HDU 1686 Oulipo（KMP）

传送门： http://acm.hdu.edu.cn/showproblem.php?pid=1686

Problem 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 word W and a text T, count the number of occurrences of W in T. All the consecutive characters of W must exactly match consecutive characters of T. 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 string W).
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 word W in the text T.

Sample Input
3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

Sample Output
1
3
0

其实和普通入门kmp没区别 其他题是求在模式串在文本串的第几个位置
这个求的是 模式串在文本串中有几个，

那么我们只需要在kmp找到这个串 ，加1

然后再将j的值 初始为当前next[j]的值 即假设回到当前 没有找到的状态继续往后进行
code：

#include <string.h>#include <stdio.h>//#include <bits/stdc++.h>#define Max 1000005char a[Max];char b[Max];int next[Max];int m, n;int sum;void getnext(){    int j=0, k=-1;    next[0] = -1;    while (j<m)    {        if (k==-1||b[j]==b[k])        {            j++;            k++;            next[j] = k;        }        else            k = next[k];    }}int kmp(){    int i=0, j=0;    getnext();    while (i<n)    {        if (j==-1||a[i]==b[j])        {            i++;            j++;        }        else            j = next[j];        if (j==m)        {            sum++;            j=next[j];        }    }    return sum;}int main(){    int N;    scanf("%d",&N);    while (N--)    {        sum=0;        //int n ,m;        scanf("%s%s",b,a);        m = strlen(b);        n = strlen(a);        int t = kmp();            printf ("%d\n",sum);    }    return 0;}