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：

 1 #include<cstdio>
 2 #include<string.h>
 3 using namespace std;
 4 typedef unsigned int ui;
 5 typedef long long ll;
 6 typedef unsigned long long ull;
 7 #define pf printf
 8 #define mem(a,b) memset(a,b,sizeof(a))
 9 #define prime1 1e9+7
10 #define prime2 1e9+9
11 #define pi 3.14159265
12 #define lson l,mid,rt<<1
13 #define rson mid+1,r,rt<<1|1
14 #define scand(x) scanf("%llf",&x) 
15 #define f(i,a,b) for(int i=a;i<=b;i++)
16 #define scan(a) scanf("%d",&a)
17 #define dbg(args) cout<<#args<<":"<<args<<endl;
18 #define inf 0x3f3f3f3f
19 #define maxn 1000010
20 int n,m,t;
21 ull Hash[maxn],h[maxn];
22 char a[maxn],b[maxn];
23 const int p=131;
24 void init()
25 {
26     h[0]=1;
27     f(i,1,maxn-1)
28     {
29         h[i]=h[i-1]*p;
30     }
31  } 
32  
33 int main()
34 {
35     //freopen("input.txt","r",stdin);
36     //freopen("output.txt","w",stdout);
37     //std::ios::sync_with_stdio(false);
38     scan(t); 
39     init();
40     while(t--)
41     {
42         scanf("%s%s",&a,&b);
43         int lena=strlen(a);
44         int lenb=strlen(b);
45         int ans=0;
46         int hasha=a[0]-'a',hashb;
47         f(i,1,lena-1)
48         {
49             hasha=hasha*p+a[i]-'a';
50         }
51         Hash[0]=b[0]-'a';
52         f(i,1,lenb-1)
53         {
54             Hash[i]=Hash[i-1]*p+b[i]-'a';
55         }
56         f(i,0,lenb-lena)
57         {
58             int l=i;
59             int r=l+lena-1;
60             hashb=Hash[r]-Hash[l-1]*h[lena];
61             if(hasha==hashb)ans++;
62         //    dbg(ans);
63         }
64         pf("%d\n",ans);
65     }
66  }

 

posted @ 2020-03-20 22:30  WA自动机~  阅读(128)  评论(0)  编辑  收藏  举报