Oulipo（KMP哈希）

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

解题思路

基本上是哈希和KMP的板子题，在这里主要讲下KMP：主要就是维护一个next数组。
先给个列子比如
0 0 1 2 3 4 5
A Z A Z A Z A 下面是标号，上面是next数组，**while(s[i]！=s[next[i-1]]&&next[i-1]>0) next[i-1]=next[next[i-1]-1]； **if(s[i]==s[next[i-1]]) next[i]=next[i-1]+1;else next[i]=0 **

0 1 2 3 4 5 6
这个有什么用那，别着急看这个例子

0	0	1	0	1	2	3	2	3	2	3
A	Z	A	$	A	Z	A	Z	A	Z	A
0	1	2	3	4	5	6	7	8	9	10

我们让子串加上母串再求next数组就得到了这么的答案，等等我们发现了s[6]=3 ， s[8]=3 ，s[10]=3，
正好是3个，答案也是3个（amazing），我讲一下next[7]是怎么求的，求next[7]我们要看s[7]是否等于s[next[6]]很明显s[7]=z,s[next[6]]=$,不成立，怎么办，看上面的式子next[6]=next[next[6]-1]=1,在比较s[next[6]]与next[7]是否相等，一看相等就加一next[7]=next[6]+1=2。自己用手模拟一下。

#include<bits/stdc++.h>
using namespace std;
const int maxn=1e5+10;
string s1,s2;
vector<int> getnxt(string t)
{int len= t.size();vector<int> nxt(len);for(int i=1;i<len;i++){int j=nxt[i-1];while(t[i]!=t[j]&&j>0) j=nxt[j-1];//求next数组 if(t[i]==t[j]) j++;nxt[i]=j;}return nxt;
}int main()
{ios::sync_with_stdio(0);//关下同步不然会超时cin.tie(0);cout.tie(0); int t;cin>>t;while(t--){cin>>s1>>s2;int len1=s1.size();string s3=s1+'#'+s2;//这个构造一个新的字符串 vector<int> nxt=getnxt(s3);int len2=s3.size();int k=0;for(int i=len1+1;i<len2;i++){if(nxt[i]==len1)//枚举长度 {k++;}}printf("%d\n",k);   }return 0;
}

Oulipo（KMP哈希）相关推荐

Oulipo (KMP算法）
Oulipo (KMP算法) 题目链接:HDU-1686 题目: Oulipo Problem Description The French author Georges Perec (1936–19 ...
POJ 3461 字符串匹配（KMP / 哈希（有推导））
文章目录 1. 题目 1.1 题目链接 1.2 题目大意 2. Accepted代码 2.1 KMP解法 2.2 哈希法(有推导过程) 1. 题目 1.1 题目链接 http://poj.org/pr ...
Oulipo[字符串哈希]
题目 The French author Georges Perec (1936–1982) once wrote a book, La disparition, without the letter ...
F - Oulipo(kmp经典模板题）！！！
The French author Georges Perec (1936–1982) once wrote a book, La disparition, without the letter 'e ...
HDU - 1686 Oulipo KMP
Oulipo Problem Description The French author Georges Perec (1936–1982) once wrote a book, La dispari ...
POJ - Oulipo(KMP)
题目链接:http://poj.org/problem?id=3461 Time Limit: 1000MS Memory Limit: 65536K Description The French a ...
Oulipo(kmp算法)
题目意思就是找子串在一个长串中出现的次数. 因为数据较大,一般的做法都超时,看了看kmp算法,用这个算法做的.这个算法最难的就是求那个next数组吧. #include<iostream> ...
POJ3461 Oulipo ——KMP算法——Pku3461
建议大家学一学比较巧妙的KMP算法吧,很有意思.推荐个题目:POJ3167 Cow Patterns 题解我会发在本博里. 这个KMP就木有什么好说的了吧,大家找百度百科学一下就可以了~ CODE P ...
HDU 1618 Oulipo KMP解决问题的方法
鉴于两个字符串,寻找一个字符串的频率,另一个字符串出现. 原版的kmp另一个陷阱.以下凝视了,标不是踩着好,有加班一定几率,也有机会错误,根据不同的字符串可以是详细. 变化看起来像一个,kmp速度是非 ...

Oulipo（KMP哈希）

解题思路

Oulipo（KMP哈希）相关推荐

最新文章

热门文章