KMP

 1 //Next数组计算
 2 void CalNext(const char* p, int* next)
 3 {
 4     int i = 0, j = -1;
 5     next[0] = -1;
 6     while (p[i] != ‘\0‘)
 7     {
 8         if (j < 0 || p[i] == p[j])
 9         {
10             i++, j++;
11             next[i] = j;
12         }
13         else
14             j = next[j];
15     }
16 }
17 
18 //利用Next数组的KMP
19 int KMPStr(char* haystack, const char* needle)
20 {
21     int res = 0;
22     int lenS = strlen(haystack);
23     int lenP = strlen(needle);
24     int i = 0, j = 0;
25     int* next = new int[lenP+1];
26     CalNext(needle, next);
27 
28     while (i < lenS && j < lenP)
29     {
30         if (j < 0 || haystack[i] == needle[j])
31         {
32             i++, j++;
33         }
34         else
35             j = next[j];
36 
37         if (j == lenP) {
38             j = next[j];
39             res++;
40         }
41     }
42 
43     delete[] next;
44     return res;
45 }