Oulipo
| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 47077 | Accepted: 18734 |
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
查找一个模式串在其他串中出现的次数；
扩展KMP即可
#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;
#define MAXN 1000050
char s[MAXN];
char t[MAXN];
int l1,l2;
int nxt[MAXN];
void getnxt()
{
int j,k;
j=0;
k=-1;
nxt[0]=-1;
while(j<l2)
{
if(k==-1||t[j]==t[k])
{
nxt[++j]=++k;
}
else k=nxt[k];
}
}
int kmpcount()
{
int ans=0;
int i=0;
int j=0;
if(l1==1&&l2==1)
{
if(s[0]==t[0])
return 1;
else return 0;
}
getnxt();
for(i=0;i<l1;i++)
{
while(j>0&&s[i]!=t[j])
{
j=nxt[j];
}
if(s[i]==t[j])
{
j++;
}
if(j==l2)
{
ans++;
j=nxt[j];
}
}
return ans;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int T;
cin>>T;
while(T--)
{
cin>>t>>s;
l1=strlen(s);
l2=strlen(t);
cout<<kmpcount()<<endl;
}
return 0;
}