2013
12-12

# 九度-1094-String Matching[解题代码]

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.

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.

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

abababab abab

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？