首页 > ACM题库 > 九度OJ > 九度-1094-String Matching[解题代码]
2013
12-12

九度-1094-String Matching[解题代码]

题目来源:2006年上海交通大学计算机研究生机试真题

题目描述:

    Finding all occurrences of a pattern in a text is a problem that arises frequently in text-editing programs.
    Typically,the text is a document being edited,and the pattern searched for is a particular word supplied by the user.  
    We assume that the text is an array T[1..n] of length n and that the pattern is an array P[1..m] of length m<=n.We further assume that the elements of P and  T are all alphabets(∑={a,b…,z}).The character arrays P and T are often called strings of characters.  
    We say that pattern P occurs with shift s in the text T if 0<=s<=n and T[s+1..s+m] = P[1..m](that is if T[s+j]=P[j],for 1<=j<=m).  
    If P occurs with shift s in T,then we call s a valid shift;otherwise,we calls a invalid shift. 
    Your task is to calculate the number of vald shifts for the given text T and p attern P.

输入:

   For each case, there are two strings T and P on a line,separated by a single space.You may assume both the length of T and P will not exceed 10^6.

输出:

    You should output a number on a separate line,which indicates the number of valid shifts for the given text T and pattern P.

样例输入:
abababab abab
样例输出:
3

cpp 代码如下:
#include <iostream>
#include <string>
using namespace std;
string str, strfind;
int main()
{
	int start,cnt;
	while(cin >> str >> strfind){
		start = 0;
		cnt = 0;
		while( (start = str.find(strfind, start)) != string::npos)
		{
			start ++;
			cnt ++;
		}
		cout << cnt << endl;
	}

	return 0;
}
/**************************************************************
	Problem: 1094
	User: coder
	Language: C++
	Result: Accepted
	Time:130 ms
	Memory:3052 kb
****************************************************************/


  1. 其实国内大部分公司对算法都不够重视。特别是中小型公司老板根本都不懂技术,也不懂什么是算法,从而也不要求程序员懂什么算法,做程序从来不考虑性能问题,只要页面能显示出来就是好程序,这是国内的现状,很无奈。

  2. 我还有个问题想请教一下,就是感觉对于新手来说,递归理解起来有些困难,不知有没有什么好的方法或者什么好的建议?