Oulipo (HDU_1686) KMP

Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 8934    Accepted Submission(s): 3614

Problem 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

 

题目大意：字符串匹配。给出主串和模式串，求可以从主串中匹配出多少模式串。

解题思路：KMP。在kmp函数中，每成功匹配一次，计数加一，并且将j = next[j];

代码如下：

#include"iostream"#include"cstdio"#include"cstring"using namespace std;const int maxn = 1000005;const int maxm = 10005;char s[maxn],p[maxm];int Next[maxm];void MakeNext(int m){Next[0] = -1;//-1 表示没有已匹配的串中没有符合要要求的 int i = 0,j = -1;//i表示主串的指针，j表示模式串的指针 while(i < m){//i不回溯，不断向后移动 if(j == -1 || p[i] == p[j]){  i ++ , j ++;//两串当前位置相等，比较下一位 if(p[i] != p[j]) Next[i] = j;else Next[i] = Next[j];}else j = Next[j];}}int KMP(int n,int m){int i = 0,j = 0,cnt = 0;while(i < n && j < m){if(s[i] == p[j] || j == -1){i ++,j ++;if(j == m){//成功匹配 cnt ++;j = Next[j];}}else j = Next[j];}return cnt;}int main(){int n,m,cas;scanf("%d",&cas);while(cas --){scanf("%s%s",&p,&s);n = strlen(s);m = strlen(p);if(m > n) printf("0\n");else{MakeNext(m);printf("%d\n",KMP(n,m));}}return 0;}