B - Oulipo（KMP）

B -Oulipo

Time Limit:1000Memory Limit:6553664bit IO Format:%I64d & %I64u

SubmitStatusPracticePOJ 3461

use MathJax to parse formulas

Description

'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 wordWand a textT, count the number of occurrences ofWinT. All the consecutive characters of W must exactly match consecutive characters ofT. 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 wordW, a string over {'A','B','C', …,'Z'}, with 1 ≤ |W| ≤ 10,000 (here |W| denotes the length of the stringW).
• One line with the textT, 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 wordWin the textT.

Sample Input

3 BAPC BAPC AZA AZAZAZA VERDI AVERDXIVYERDIAN

Sample Output

1 3 0

题意：找给定的串里有多少个子串

此题用多了strlen以后会超时

代码：

#include <iostream> #include<stdio.h> #include<string.h> #include<algorithm> using namespace std; char a[1000055]; char b[1000055]; int f[1000055]; void getn() { f[0]=-1; int l1=strlen(a); for(int i=1;i<l1;i++) { int j=f[i-1]; while(a[j+1]!=a[i]&&(j>=0)) j=f[j]; if(a[j+1]==a[i]) f[i]=j+1; else f[i]=-1; } } int kmp() { int ans=0; getn(); int i=0,j=0,l=strlen(a),l2=strlen(b); while(j<l2) { if(a[i]==b[j]) { i++; j++; if(i==l) { ans++; i=f[i-1]+1; //样例为asa和asasasa的情况 } } else if(i==0) //这里必须有j++，否则当样例是asd和basd时，母串的第一位b过不去 j++; else i=f[i-1]+1; //这里必须是f[i-1]因为如果子串是aabb，那么f数组是-1 0 -1 -1另一个是aaabb

会造成不匹配， } return ans; } int main() { int t,ans; cin>>t; while(t--) { scanf("%s",&a); scanf("%s",&b); ans=kmp(); printf("%d\n",ans); } return 0; }

文章来源: B - Oulipo（KMP）