zoj 1500 Pre

#include <iostream>#include <cstdio>#include <string.h>using namespace std;int k;int C( int m,int n ){    int i,mul=1;    for( i=0;i<n;i++ )        mul*=(m-i);    for( i=n;i>=1;i-- )        mul/=i;    return mul;}int solve( int m,char *pre,char *post ){    int i=1,j=0,re=1,son=0;     while( i<m )    {        while( post[j]!=pre[i] ) j++;        son++;        re*=solve( j+2-i,pre+i,post+i-1 );        i=j+2;    }    return re*C( k,son );}int main(){    char pre[30],post[30];    while( scanf( "%d",&k ) && k )    {        scanf( "%s%s",pre,post );        printf( "%dn",solve( strlen(pre),pre,post ) );    }    return 0;}