POJ 3461 Oulipo(KMP经典)
2017-07-17 21:21
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原题
Oulipo
Time Limit:1000MS Memory Limit:65536KB 64bit IO Format:%I64d & %I64uDescription
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
3BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN
Sample Output
13
0
题意
输出第一个字符串在第二个字符串中出现的次数。注意匹配成功后要返回next涉及知识及算法
线性时间字符串匹配算法KMP代码
#include <iostream> #include <cstdio> #include <string.h> using namespace std; int next[10005]; char str1[1000005],str2[10005]; int cnt; void get_next(int len2) //生成next数组 { int i=0,j=-1; next[0]=-1; while(i<len2) { if(j==-1||str2[i]==str2[j]) { next[++i]=++j; } else { j=next[j]; } } } void kmp(int len1,int len2) //kmp算法 { int i=0,j=0; get_next(len2); while(i<len1) { if(j==-1||str1[i]==str2[j]) { ++i; ++j; } else { j=next[j]; } if(j==len2) { cnt++; j=next[j]; } } } int main() { //freopen("in.txt","r",stdin); //freopen("out.txt","w",stdout); int n; int len1,len2; scanf("%d",&n); getchar(); while(n--) { gets(str2); gets(str1); len1=strlen(str1); len2=strlen(str2); cnt=0; kmp(len1,len2); printf("%d\n",cnt); } return 0; }
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