POJ3461 Oulipo(字符串匹配KMP)

题目：

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Oulipo

Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 40409 Accepted: 16253

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

Source

BAPC 2006 Qualification

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思路：

KMP模板题，求的是子串在原串中出现的次数

代码：

#include<cstdio>#include<cstring>#include<string>#include<set>#include<iostream>#include<stack>#include<queue>#include<vector>#include<algorithm>#define mem(a,b) memset(a,b,sizeof(a))#define inf 0x3f3f3f3f#define mod 10000007#define debug() puts("what the fuck!!!")#define N 1000010#define ll longlongusing namespace std;char s1[N],s2[N];int next[N];int len1,len2,n,m;void get_next(){    int j=0,k=-1;    next[0]=-1;    while(j<len1)    {        if(k==-1||s1[j]==s1[k])            next[++j]=++k;        else            k=next[k];    }}int KMP_count(){    int ans=0;    int i,j=0;    if(len1==1&&len2==1)    {        if(s1[0]==s2[0])            return 1;        else            return 0;    }    get_next();    for(int i=0; i<len2; i++)    {        while(j>0&&s2[i]!=s1[j])            j=next[j];        if(s1[j]==s2[i])            j++;        if(j==len1)        {            ans++;            j=next[j];        }    }    return ans;}int main(){    int t;    scanf("%d",&t);    while(t--)    {        scanf("%s%s",s1,s2);        len1=strlen(s1);        len2=strlen(s2);        printf("%d\n",KMP_count());    }    return 0;}