题目链接：http://poj.org/problem?id=3461
| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 23559 | Accepted: 9437 |
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:
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
题意：
寻找子串在母串出现的次数！
代码如下：
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
using namespace std;
#define MAXN 1000017
int next[MAXN];
char s1[MAXN],s2[MAXN];
int k;
void getnext( char T[],int len)
{
int i = 0, j = -1;
next[0] = -1;
while(i < len)
{
if(j == -1 || T[i] == T[j])
{
i++,j++;
next[i] = j;
}
else
j = next[j];
}
}
void KMP(int len1, int len2 )
{
int i = 0, j = 0 ;
k=0;
next[0] = -1 ;
while( i < len1 && j < len2 )
{
if( j == -1 || s1[i] == s2[j])
{
i++;j++;
}
else
j = next[j];
if( j == len2)
{
k++;
j = next[j];
}
}
}
int main()
{
int t;
scanf("%d",&t);
getchar();
while(t--)
{
gets(s2);//待匹配子串
int len2 = strlen(s2);
getnext(s2,len2);
gets(s1);//总串（母串）
int len1 = strlen(s1);
KMP(len1, len2);
printf("%d\n",k);
}
return 0;
}
poj 3461 Oulipo（KMP模板题）,布布扣,bubuko.com
原文地址：http://blog.csdn.net/u012860063/article/details/38562751
