KMP -- POJ3461

    KMP -- POJ3461解题报告

问题描述：给出字符串P和字符串T，问字符串P在字符串T中出现的次数

Sample Input

3

BAPC

BAPC

AZA

AZAZAZA

VERDI

AVERDXIVYERDIAN



Sample Output

1

3

0

简单KMP应用， 代码如下：

 1 //poj3461解题报告

 2 #include<iostream>

 3 using namespace std;

 4 

 5 char T[1000005], P[10005];

 6 int len1, len2;

 7 int next[10005];

 8 

 9 void getnext(char P[])

10 {

11     int i = 0, j = -1;

12     next[0] = -1;

13     while(i < len2)

14     {

15         if(j == -1 || P[i] == P[j])

16         {

17             i ++;

18             j ++;

19             next[i] = j;

20         }

21         else

22             j = next[j];

23     }

24 }

25 

26 int kmp()

27 {

28     int i = 0, j = 0;

29     int count = 0;

30     for(i = 0; i < len1; i ++)

31     {

32         while(j > 0 && T[i] != P[j])

33             j = next[j];

34         if(T[i] == P[j])

35             j++;

36         if(j == len2)

37         {

38             count ++;

39             j = next[j];

40         }

41     }

42     return count;

43 }

44 

45 int main()

46 {

47     int t;

48     while(scanf("%d", &t) != EOF)

49     {

50         for(int i = 1; I <= t; i ++)

51         {

52             scanf("%s%s", P, T);

53             int count = 0;

54             len1 = strlen(T);

55             len2 = strlen(P);

56             getnext(P);

57             int k = kmp();

58             printf("%d\n", k);

59         }

60     }

61     return 0;

62 }