Oulipo

最新推荐文章于 2021-12-11 18:48:23 发布

veget_chicken

最新推荐文章于 2021-12-11 18:48:23 发布

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分类专栏： kmp 文章标签： kmp

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本文介绍了一个基于KMP算法的应用案例，旨在解决特定字符串匹配问题。通过实现KMP算法的计数功能，快速准确地找出一个给定单词在文本中出现的次数。

链接：http://acm.hust.edu.cn/vjudge/problem/10368/origin

题目：

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.

题意：有两个字符串，问a串在b串种出现了几次。

分析：简单的kmp题。代板子就行了

题解：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <string>
#include <cstring>
#include <functional>
#include <cmath>
#include <cctype>
#include <cfloat>
#include <climits>
#include <complex>
#include <deque>
#include <list>
#include <set>
#include <utility>
#define rt return 0
#define fr freopen("in.txt","r",stdin)
#define fw freopen("out.txt","w",stdout)
#define ll long long
#define detie ios_base::sync_with_stdio(false);cin.tie(false)
using namespace std;

int Next[1000010];
void getNext(string s)
{
	int j = 0;
	int k = -1;
	Next[0] = -1;
	while (j<s.size())
	{
		if (k == -1 || s[j] == s[k])
			Next[++j] = ++k;
		else
			k = Next[k];
	}
}

int KMP_Count(string a, string b)
{
	int sum = 0;
	int i = 0;
	int j = 0;
	getNext(b);
	while (i < a.size())
	{
		if (j == -1 || a[i] == b[j])
		{
			i++;
			j++;
		}
		else
			j = Next[j];
		if (j == b.size())
		{
			sum++;
		}
	}
	return sum;
}

int main()
{
	//fr;
	detie;
	int n;
	cin >> n;
	while (n--)
	{
		string a, b;
		cin >> a >> b;
		cout << KMP_Count(b, a) << endl;
	}
	rt;
}