poj-3461(Oulipo)(kmp())
| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 32911 | Accepted: 13321 |
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題意：求子串在主串中出現的次數。
以第二個樣例爲例，子串前三個字符和主串的前3個字符匹配。當j=3，子串中不存在字符所以；c1[3]!=c2[3]，j=nest[3]=1，然後c1[3]==c2[1],繼續往下匹配。
My solution:
/*2016.4.11*/
#include<cstdio>
#include<cstring>
char c1[1001000],c2[10100];
int nest[10100],len;
void getnest()
{
int i,j,k;
len=strlen(c2);
i=0;j=-1;
nest[i]=j;
while(i<len)
{
if(j==-1||c2[i]==c2[j])
{
i++,j++;
nest[i]=j;
}
else
j=nest[j];
}
}
void kmp()
{
int i,j,k,len2,cnt=0;
len2=strlen(c1);
i=0,j=0;
getnest();
while(i<len2)
{
if(j==-1||c1[i]==c2[j])
{
i++;
j++;
if(len==j)
cnt++;//記錄子串出現的次數
}
else
j=nest[j];
}
printf("%d\n",cnt);
}
int main()
{
int i,j,k,n;
scanf("%d",&n);
while(n--)
{
scanf("%s",c2);
scanf("%s",c1);
kmp();
}
return 0;
}