ACM -- 算法小结（四）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：

 //poj3461解题报告
 #include<iostream>
 using namespace std;

 char T[], P[];
 int len1, len2;
 int next[];

 void getnext(char P[])
 {
     int i = , j = -;
     next[] = -;
     while(i < len2)
     {
         if(j == - || P[i] == P[j])
         {
             i ++;
             j ++;
             next[i] = j;
         }
         else
             j = next[j];
     }
 }

 int kmp()
 {
     int i = , j = ;
     int count = ;
     for(i = ; i < len1; i ++)
     {
         while(j >  && T[i] != P[j])
             j = next[j];
         if(T[i] == P[j])
             j++;
         if(j == len2)
         {
             count ++;
             j = next[j];
         }
     }
     return count;
 }

 int main()
 {
     int t;
     while(scanf("%d", &t) != EOF)
     {
         for(int i = ; I <= t; i ++)
         {
             scanf("%s%s", P, T);
             int count = ;
             len1 = strlen(T);
             len2 = strlen(P);
             getnext(P);
             int k = kmp();
             printf("%d\n", k);
         }
     }
     return ;
 }