POJ 3461 Oulipo【KMP】

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

3BAPCBAPCAZAAZAZAZAVERDIAVERDXIVYERDIAN

Sample Output

130

/*    题意：求模式串在字符串中出现的次数    类型：KMP    分析：稍微修改一下KMP模版，对于匹配成功时答案数+1，并且使得模式串再次左移          已匹配-对应的Next值即可*/#include<cstdio>#include<cstring>#include<algorithm>#include <iostream>#include <string>using namespace std;const int maxn = 1e6+5;int Next[maxn];char s[maxn],p[maxn];int n,m;void getNext(int m){    int i=0,j=-1;    Next[0]=-1;    while(i < m){        if(j == -1 || p[i] == p[j])            Next[++i] = ++j;        else            j=Next[j];    }}int Kmp(int n,int m){    getNext(m);    int i = 0,j = 0;    int ans = 0;    while(i < n && j < m){        if(j == -1 || s[i] == p[j]){            i++;            j++;        }        else j=Next[j];        if(j>=m)ans++,j=Next[j];    }    return ans;}int main(){    int T;    scanf("%d",&T);    while(T--){        scanf("%s%s",p,s);        n=strlen(s);m=strlen(p);        int ans=Kmp(n,m);        printf("%d\n",ans);    }    return 0;}