字符串哈希

#include
#define ull unsigned long long
using namespace std;
const ull B = 1e8+7;
const int MAXN = 5010;
char a[MAXN],b[MAXN];
int find()
{
    int al=strlen(a),bl=strlen(b);
    if(al>bl)return -1;
    ull t=1,ah=0,bh=0;
    for(int i=0;i表示一个字符串