Problem 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 基本算是模板,看代码即可: #include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
const int N=1000005;
char s[N],t[N];
int nex[N];//记录最长后缀
int l1,l2;
void get_next()
{
int i=0,j=-1;
nex[0]=-1;
while(i<l2)
{
if(j==-1||t[i]==t[j])
nex[++i]=++j;
else
j=nex[j];
}
}
int kmp()
{
memset(nex,0,sizeof(nex));
get_next();
int i=0,j=0,ans=0;
while(i<l1)
{
if(j==-1||s[i]==t[j])
{
i++;
j++;
}
else
j=nex[j];
if(j>=l2)//只需要在模板上加上这一步即可
ans++;
}
return ans;
}
int main()
{
int T;
scanf("%d",&T);
while(T--)
{
int i,j;
scanf("%s%s",t,s);
l1=strlen(s);//主串长度
l2=strlen(t);//子串长度
printf("%d\n",kmp());
}
return 0;
} |