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

来源：

2006年上海交通大学计算机研究生机试真题

答疑：

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#include <stdio.h> 
#include <string.h> 
  
char s1[1000001]; 
char s2[1000001];
 
int main() 
{
    while(scanf("%s%s",s1,s2)!=EOF) 
    { 
        int ans=0; 
        char *s=s1; 
        while(s=strstr(s,s2)) 
        { 
            s++; 
            ans++; 
        } 
        printf("%d\n",ans); 
    } 
    
    return 0; 
}
/**************************************************************
    Problem: 1094
    User: vhreal
    Language: C
    Result: Accepted
    Time:20 ms
    Memory:2868 kb
****************************************************************/