poj 3461 Oulipo ----KMP,字符串处理
2012-08-10 16:04
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Oulipo
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
Sample Output
题目大意: 赤裸裸的KMP。就是求 子串 在 主串中出现的次数。
题目思路: KMP 。KMP 重要的就是 next数组的建立。next数组就是对 子串 在与 主串匹配时加了预处理。
使得匹配效率提升了很多。避免了不必要的匹配。预处理也就是求next数组这里可能难理解一点
http://baike.baidu.com/view/574553.htm
Oulipo
Time Limit: 1000MS | Memory Limit: 65536K | |
Total Submissions: 12706 | Accepted: 5075 |
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
题目大意: 赤裸裸的KMP。就是求 子串 在 主串中出现的次数。
题目思路: KMP 。KMP 重要的就是 next数组的建立。next数组就是对 子串 在与 主串匹配时加了预处理。
使得匹配效率提升了很多。避免了不必要的匹配。预处理也就是求next数组这里可能难理解一点
http://baike.baidu.com/view/574553.htm
#include; #include; int next[10050]; char p[10050],t[1001000]; void get_next(char *a,int len); int main() { // freopen("in.txt","r",stdin); int n,lenp,lent,i,j; while(scanf("%d",&n)!=EOF) { while(n--) { int sum=0; i=0,j=0; scanf("%s%s",p,t); lenp=strlen(p); lent=strlen(t); get_next(p,lenp); //求next数组 // for(i=0;i<lenp;i++) // printf("%d ",next[i]); while(i<lent) //匹配 { if(j==-1|| t[i]==p[j]) { i++; j++; if(j==lenp) { sum++; j=next[j]; } } else j=next[j]; } printf("%d\n",sum); } } return 0; } void get_next(char *a,int len) { int i=0,j=-1; next[0]=-1; while(i<len) //很巧妙的方法。 { if(j==-1 || a[i]==a[j]) { i++; j++; next[i]=j; } else j=next[j]; } }
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