POJ3461一道kmp题，字符串Hash也可

题目链接：http://icpc.njust.edu.cn/Problem/Pku/3461/

代码如下：

 #include<cstdio>
 #include<string.h>
 using namespace std;
 typedef unsigned int ui;
 typedef long long ll;
 typedef unsigned long long ull;
 #define pf printf
 #define mem(a,b) memset(a,b,sizeof(a))
 #define prime1 1e9+7
 #define prime2 1e9+9
 #define pi 3.14159265
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define scand(x) scanf("%llf",&x)
 #define f(i,a,b) for(int i=a;i<=b;i++)
 #define scan(a) scanf("%d",&a)
 #define dbg(args) cout<<#args<<":"<<args<<endl;
 #define inf 0x3f3f3f3f
 #define maxn 1000010
 int n,m,t;
 ull Hash[maxn],h[maxn];
 char a[maxn],b[maxn];
 const int p=;
 void init()
 {
     h[]=;
     f(i,,maxn-)
     {
         h[i]=h[i-]*p;
     }
  } 

 int main()
 {
     //freopen("input.txt","r",stdin);
     //freopen("output.txt","w",stdout);
     //std::ios::sync_with_stdio(false);
     scan(t);
     init();
     while(t--)
     {
         scanf("%s%s",&a,&b);
         int lena=strlen(a);
         int lenb=strlen(b);
         int ans=;
         int hasha=a[]-'a',hashb;
         f(i,,lena-)
         {
             hasha=hasha*p+a[i]-'a';
         }
         Hash[]=b[]-'a';
         f(i,,lenb-)
         {
             Hash[i]=Hash[i-]*p+b[i]-'a';
         }
         f(i,,lenb-lena)
         {
             int l=i;
             int r=l+lena-;
             hashb=Hash[r]-Hash[l-]*h[lena];
             if(hasha==hashb)ans++;
         //    dbg(ans);
         }
         pf("%d\n",ans);
     }
  }