[POJ 3461] Oulipo & KMP模板

Oulipo

Time Limit: 1000ms, Memory Limit: 65536K

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

Source

【题解】

KMP模板题，都没有实现过KMP，这是第一次实现，主要就是getnext的实现，KMP复杂度O(n+m)，这题总复杂度O(T(n+m))

#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;
int next[100010];
char s[1000010],p[10010];
int slen,plen;
void getnext() {   
    int i=0,j=-1;
    next[0]=-1;
    while(i<plen) {
        if(j==-1||p[i]==p[j]) next[++i]=++j;
        else j=next[j];
    }
}  
int kmpsearch() {
    slen=strlen(s);plen=strlen(p);
    int ans=0;
    int i=0,j=0;
    getnext();
    while(i<slen&&j<plen) {
        if (j==-1||s[i]==p[j]) ++i,++j;
        else j=next[j];
        if (j==plen) ans++,j=next[j];
    }
    return ans;
}
int main() {
    int t;
    scanf("%d",&t);
    while(t--)
        scanf("%s%s",p,s),printf("%d
",kmpsearch());
    return 0; 
}

WA了好多次，谢谢ysy大聚聚