POJ - 3461 Oulipo（KMP模板题）

B - Oulipo

Time Limit:1000MS     MemoryLimit:65536KB     64bit IO Format:%I64d& %I64u

Submit Status Practice POJ 3461

Description

The Frenchauthor Georges Perec (1936–1982) once wrote a book, La disparition, without theletter 'e'. He was amember of the Oulipo group. A quote from the book:

Tout avait Pairnormal, mais tout s’affirmait faux. Tout avait Fair normal, d’abord, puissurgissait l’inhumain, l’affolant. Il aurait voulu savoir où s’articulaitl’association qui l’unissait au roman : stir son tapis, assaillant à toutinstant 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 commandanttout, où s’abolissait la raison : tout avait l’air normal mais…

Perec wouldprobably have scored high (or rather, low) in the following contest. People areasked to write a perhaps even meaningful text on some subject with as fewoccurrences of a given “word” as possible. Our task is to provide the jury witha program that counts these occurrences, in order to obtain a ranking of thecompetitors. These competitors often write very long texts with nonsensemeaning; a sequence of 500,000 consecutive 'T's is not unusual. And they never use spaces.

So we want toquickly find out how often a word, i.e., a given string, occurs in a text. Moreformally: given the alphabet {'A', 'B', 'C', …, 'Z'} and two finitestrings over that alphabet, a word W and a text T,count the number of occurrences of W in T. All theconsecutive characters of W must exactly match consecutive characters of T.Occurrences may overlap.

Input

The first lineof 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 testcase in the input file, the output should contain a single number, on a singleline: the number of occurrences of the word W in thetext T.

Sample Input

3

BAPC

BAPC

AZA

AZAZAZA

VERDI

AVERDXIVYERDIAN

Sample Output

1

3

0

 KMP模板题。

#include<iostream>#include<string>#include<cstring>#include<cstdio>#include <stdlib.h>          //题目大意:   给出主串和模式串，求模式串在主串中出现的次数(部分可以重合)using namespace std;         //暴力匹配自然会 TLE                             //用KMP，利用上next[ ]数组的含义，每次不全部退出，而是退出部分j=next[ j ]int nextl[1000000];char str[1000000];char word[100000];int len;int Slen;void get_nextlen(int n){int i = 0, j = -1;nextl[0] = -1;while (i <= n){if (j == -1 || word[i] == word[j]){j++; i++;nextl[i] = j;}else j = nextl[j];}return;}int Kmp(int u){int i = u - 1, j = -1, m = 0;     //字符串从0开始存储的while (i <= Slen){if (j == -1 || str[i] == word[j]){i++; j++;}elsej = nextl[j];if (j >= len)         //**注意这里要j--,i--,因为上面匹配成功了i和j的值加多了1{m++;j--; i--;j = nextl [j];      //返回}}return m;}int main(){int casen;cin >> casen;while (casen--){memset(nextl, 0, sizeof(nextl));cin >> word;cin >> str;len = strlen(word);Slen = strlen(str);get_nextlen(len);int ans = Kmp(0);          //Kmp从第一个字符开始匹配cout << ans << endl;}}