kmp字符串匹配算法

来源：互联网发布：网络社区营销案例编辑：程序博客网时间：2024/04/25 09:46

[ code=C C++ ][#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void KmpMatcher(char *sourceText, char *str);
void ComputePrefix(int *pi, char *str);

int main(int argc, char *argv[])
{
char sourceText[] = "DocumentsandSettingsAdministratorLocalSettingsTemporaryInternetFiles";
char str0[] = "Administrator";
char str1[] = "Temporary";
char str2[] = "LocalSettings";
KmpMatcher(sourceText,str0);
KmpMatcher(sourceText,str1);
KmpMatcher(sourceText,str2);
return 1;
}

void KmpMatcher(char *sourceText, char *str)
{
int m = strlen(str);
int n = strlen(sourceText);
int *pi = (int *)malloc(sizeof(int)*m);
int q=-1; // 匹配到的索引号,如果为 m-1 则完全匹配一次
ComputePrefix(pi,str);

for (int i=0;i<n;i++)
{
  while(q>=0 && str[q+1]!=sourceText[i])
   q = pi[q];
  if(str[q+1] == sourceText[i])
   q++;
  if(q == m-1)
  {
   printf("%s occurs with shift %d/n",str,(i-m+1));
   q = pi[q];//继续下一次匹配
  }
}
}
void ComputePrefix(int *pi, char *str)
{
//pi(i) 表示字符串跟源字符串匹配到字符索引为i的字符后,真后缀的最长前缀的索引比如 ababa pi(4) = 2 (aba)
int m = strlen(str);
pi[0] = -1;
int k=-1;
for (int i=1;i<m;i++)
{
  while (k>=0 && str[k+1]!=str[i])
  {
   k = pi[k];
  }
  if (str[k+1] == str[i])
  {
   k++;
  }
  pi[i] = k;
}
}

[/code ]