HDU 1711 Number Sequence（KMP模板）

Posted 2020-08-29 谦谦君子，陌上其华

 

http://acm.hdu.edu.cn/showproblem.php?pid=1711

这道题就是一个KMP模板。

 1 #include<iostream> 
 2 #include<cstring>
 3 using namespace std;
 4 
 5 const int maxn = 1000000+5;
 6 
 7 int n,m;
 8 
 9 int next[maxn];
10 int a[maxn], b[maxn];
11 
12 void get_next()
13 {
14     int i = -1, j = 0;
15     ::next[0] = -1;
16     while (j < m)
17     {
18         if (i == -1 || b[i] == b[j])
19             ::next[++j] = ++i;
20         else
21             i = ::next[i];
22     }
23 }
24 
25 
26 int kmp()
27 {
28     int i = 0, j = 0;
29     while (i < n)
30     {
31         if (j == -1 || a[i] == b[j])
32         {
33             i++;
34             j++;
35         }
36         else
37             j = ::next[j];
38         if (j == m)
39             return i;
40     }
41     return -1;
42 }
43 
44 int main()
45 {
46     //freopen("D:\\txt.txt", "r", stdin);
47     int t;
48     cin >> t;
49     while (t--)
50     {
51         cin >> n >> m;
52         for (int i = 0; i < n; i++)
53             cin >> a[i];
54         for (int i = 0; i < m; i++)
55             cin >> b[i];
56         get_next();
57         int k=kmp();
58         if (k!=-1)  cout << k-m+1 << endl;
59         else cout << "-1" << endl;
60     }
61     return 0;
62 }