poj 3461 Oulipo (KMP)

http://poj.org/problem?id=3461

基础KMP， 要注意一次查找完成后，到下一可查找处继续匹配，这样才能保证得到最终个数。 

code:

#include<cstdio>
#include<cstring>
char substr[10001] ;
char str[1000001] ;
int next[10001] ;
int sublen, len, ans ;
void get_next(){
    next[1] = 0 ;
    int j = 0 ;
    for(int i=2; i<=sublen; i++){
        while(j>0&&substr[j+1]!=substr[i])
            j = next[j] ;
        if(substr[j+1]==substr[i])  j ++ ;
        next[i] = j ;
    }
}
void kmp(){
    int j = 0 ;
    for(int i=1; i<=len; i++){
        while(j>0&&substr[j+1]!=str[i])
            j = next[j] ;
        if(substr[j+1]==str[i]) j ++ ;
        if(j==sublen){
            ans ++ ;
            j = next[j] ;   //一次查找完成后，到下一可查找处继续匹配
        }
    }
    printf("%d\n", ans) ;
}
int main(){
    int t ;
    scanf("%d", &t) ;
    while(t--){
        scanf("%s", substr+1) ;
        scanf("%s", str+1) ;
        ans = 0 ;
        sublen = strlen(substr+1) ;
        len = strlen(str+1) ;
        get_next() ;
        kmp() ;
    }
    return 0 ;

}