题目传送门
Oulipo
Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 22654 Accepted Submission(s): 8758
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.
Simple Input
3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN
Sample Output
1 3 0
KMP算法是字符串匹配的经典算法，效率非常高，但是难理解啊，23333；
一些讲解KMP的文章：KMP算法讲解
还可以去b站搜一下kmp，然后手动敲一下板子就应该会用吧 23333
此题是KMP的板子题；
我做题的易错点（求母串，和匹配串串长度最好求一次存起来，不然可能会TLE）
AC代码：
#include <bits/stdc++.h>
using namespace std;char pattern[10010], buffer[1000010];
int Next[10010];void get_next()
{int match = -1;int i = 0;Next[0] = -1;int len = strlen(pattern);while(i < len){if(match == -1 || pattern[match] == pattern[i]){Next[++i] = ++match;}else{match = Next[match];}}
}int kmp()
{int len1 = strlen(buffer);int len2 = strlen(pattern);int ans = 0;int i = -1, match = -1;while(i < len1){if(match == -1 || buffer[i] == pattern[match]){i++;match++;if(match == len2){ans++;}}else{match = Next[match];}}return ans;
}int main()
{int t;scanf("%d",&t);while(t--){scanf("%s %s",pattern, buffer);get_next();printf("%d\n",kmp());}return 0;
}