HDU1686 KMP

题意：一个字符串在另一个字符串中出现的次数

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 1 #include<stdio.h>

 2 #include<string.h>

 3 const int maxn = 10005;

 4 const int maxm= 1000005;

 5 int lena,lenb;

 6 char a[ maxm ],b[ maxn ];

 7 int next[ maxn ];

 8 int ans;

 9 void getNext(){

10     int j,k;

11     j=0,k=-1;

12     next[0]=-1;

13     while( j<lenb ){

14         if( k==-1||b[j]==b[k] )

15             j++,k++,next[ j ]=k;

16         else k=next[ k ];

17     }

18 }

19 int kmp(){

20     getNext();

21     int i,j;

22     i=j=0;

23     while( i<lena&&j<lenb ){

24         if( j==-1||a[i]==b[j] )

25             i++,j++;

26         else j=next[j];

27         if( j==lenb ){

28             ans++;

29             j=next[j];

30         }

31     }

32     return ans;

33 }

34 int main(){

35     int t;

36     scanf("%d",&t);

37     while(t--){

38         scanf("%s",b);

39         scanf("%s",a);

40         lena=strlen(a),lenb=strlen(b);

41         ans=0;

42         printf("%d\n",kmp());

43     }

44     return 0;

45 }