[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))
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include<stdio.h> 2 #include<string.h> 3 #include<iostream> 4 using namespace std; 5 int next[100010]; 6 char s[1000010],p[10010]; 7 int slen,plen; 8 void getnext() { 9 int i=0,j=-1; 10 next[0]=-1; 11 while(i<plen) { 12 if(j==-1||p[i]==p[j]) next[++i]=++j; 13 else j=next[j]; 14 } 15 } 16 int kmpsearch() { 17 slen=strlen(s);plen=strlen(p); 18 int ans=0; 19 int i=0,j=0; 20 getnext(); 21 while(i<slen&&j<plen) { 22 if (j==-1||s[i]==p[j]) ++i,++j; 23 else j=next[j]; 24 if (j==plen) ans++,j=next[j]; 25 } 26 return ans; 27 } 28 int main() { 29 int t; 30 scanf("%d",&t); 31 while(t--) 32 scanf("%s%s",p,s),printf("%d\n",kmpsearch()); 33 return 0; 34 }
WA了好多次,谢谢ysy大聚聚