POJ 3461 Oulipo KMP大法应用

题目：

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 text T, 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 text T.

Sample Input

3BAPCBAPCAZAAZAZAZAVERDIAVERDXIVYERDIAN

Sample Output

130

给定两个字符串a，b，求字符串a在b中出现的最大次数（b由多个a重叠拼接或者直接首尾相接而成）

用KMP中的next数组记录，每记录一次count++最后输出count即可

AC代码（c++）：

#include<cstdio>#include<iostream>#include<cstring>#include<algorithm>using namespace std;#define N 100010char s[1000010], p[N];int next[N];int lens, lenp;int KMP(){int i=0,j=0,count=0;while(i!=lens&&j!=lenp){if(s[i]==p[j]||j==-1)        {            i++;            j++;        }elsej=next[j];if(j==lenp){count++;j=next[j];}}return count;}int main(){int n;int len;int ans;scanf("%d", &n);while(n--){scanf("%s %s", p, s);lens = strlen(s);lenp = strlen(p);int i=0,j=-1;        next[0]=-1;        while(i<lenp)        {            if(j==-1||s[i]==s[j])            {                i++;                j++;                next[i]=j;            }            else                j=next[j];        }ans=KMP();printf("%d\n", ans);}return 0;}