bzoj3620 似乎在梦中见过的样子

好久没有写过KMP了，今天写个KMP练练手。
此题就是枚举左端点暴力，用KMP做到O（n^2）

#include<cstdio>
#include<cstring>
using namespace std ; 

const int MAXL = 15000 + 20 ;

char BUF_OF_T [ MAXL ] ;
int BUF_OF_F [ MAXL ] ;

class KMP {
    private :
        char * T ; 
        int * F ; 
    public : 
        KMP ( char * S ) {
            const int L = strlen ( S ) ; 
            T = BUF_OF_T ; F = BUF_OF_F ;
            strcpy ( T , S ) ; F [ 0 ] = -1 ; 
            for ( int i = 1 ; i <= L ; ++ i ) {
                int p = F [ i - 1 ] ; 
                while ( p >= 0 && T [ i ] != T [ p + 1 ] ) p = F [ p ] ;
                F [ i ] = T [ i ] == T [ p + 1 ] ? p + 1 : -1 ; 
            }
        }
        int * GET_FAIL () const { return F ; } 
} ; 

char S [ MAXL ] ; 
int K ; 
int cnt ; 
int main () {
    scanf ( "%s%d" , S , & K ) ;
    for ( int i = 0 ; S [ i ] != '' ; ++ i ) {
        char * a = S + i ;
        KMP D ( a ) ; 
        int * next = D . GET_FAIL () ; 
        const int L = strlen ( a ) ; 
        for ( int j = 1 ; j <= L ; ++ j ) { //重点：是1 <= j <= L 不是 1 <= j < L 
            int & p = next [ j ] ; 
            while ( p != -1 && next [ p ] + 1 >= K ) p = next [ p ] ;
            if ( p + 1 >= K && j + 1 - ( p + 1 ) * 2 > 0 ) cnt ++ ;
        }
    }
    printf (  "%d
" , cnt ) ; 
    return 0 ;
}