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.
InputThe 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.
OutputFor 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
#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;
char W[10010],T[1000010];
int wlen,tlen;
int next[10010];
void getNext()
{
int j,k;
j=0;
k=-1;
next[0]=-1;
while(j<wlen)
{
if(k==-1||W[j]==W[k])
{
next[++j]=++k;
}
else k=next[k];
}
}
int KMP_count()
{
int ans=0;
int i,j=0;
if(wlen==1&&tlen==1)
{
if(W[0]==T[0])return 1;
else return 0;
}
getNext();
for(i=0;i<tlen;i++)
{
while(j>0&&T[i]!=W[j])
j=next[j];
if(W[j]==T[i])j++;
if(j==wlen)
{
ans++;
j=next[j];
}
}
return ans;
}
int main()
{
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
int tcase;
scanf("%d",&tcase);
while(tcase--)
{
scanf("%s%s",&W,&T);
wlen=strlen(W);
tlen=strlen(T);
printf("%d\n",KMP_count());
}
return 0;
}
kuangbin模板求子串出现次数