KMP算法模板 求子串和模板串首先匹配的位置

 1  #include <cstdio>
 2  using namespace std;
 3
 4  const int MAXN = 1e6 + 10;
 5  int nex[MAXN];
 6  int s[MAXN], t[MAXN];
 7
 8  void get_nex(int lm)    {
 9      int i = 0, j = -1;   nex[0] = -1;
10      while (i < lm)  {
11          if (j == -1 || t[j] == t[i]) {
12              i++;    j++;    nex[i] = j;
13          }
14          else    j = nex[j];
15      }
16  }
17
18  int KMP(int ln, int lm)   {
19      get_nex (lm);
20      int i = 0, j = 0;
21      while (i < ln)  {
22          while (j != -1 && s[i] != t[j]) j = nex[j];
23          i++;    j++;
24          if (j == lm) return (i - j + 1);
25      }
26      return -1;
27  }
28
29  int main()    {
30      int T;
31     scanf ("%d", &T);
32      while (T--)   {
33          int ln, lm; scanf ("%d%d", &ln, &lm);
34          for (int i=0; i<ln; ++i)   scanf ("%d", &s[i]);
35          for (int i=0; i<lm; ++i)   scanf ("%d", &t[i]);
36          printf ("%d\n", KMP (ln, lm));
37      }
38
39      return 0;
40  }