String Matching(模式匹配)--C++实现

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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.

输入描述:

   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.

输出描述:

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

输入

abababab abab

输出

3

C++实现：

#include<iostream>
#include<string.h>
using namespace std;
int main(){
    char o[1000001];
    char f[1000001];
    while(cin>>o){
        cin>>f;
        char *s=o;
        int n=0;
        while(s=strstr(s,f)){
            s++;
            n++;
        }
        cout<<n<<endl;
    }
}