KMP字符串匹配

/*KMP字符串匹配.cpp*/

# include <stdio.h>
# include <stdlib.h>
# include <string.h>
# include <time.h>

//获得prefix数组
int* GetPrefixValue(char* strPattern, int iPatternLen);
//返回target串在pattern中第一次匹配的index
int KMPStringMatch(char* strPattern, int iPatternLen, char* strTarget, int iTargetLen, int* prefix);
int KMP(char* strPattern, char* strTarget);
//在文本中查找target串出现的位置
int SearchInTxtFile(char* fileName, char* strTarget);

int main(void)
{
	char ch;
	char str1[] = "abcabcabctasksb,abTo";
	char str2[] = "abc"; 
	double t=clock();

    printf("%d\n", KMP(str1,str2));
	printf("耗时%f毫秒!\n", (clock()-t));

	t=clock();

	printf("find %d \n", SearchInTxtFile("c:\\txt.txt", "NULL")); 
    printf("耗时%f毫秒!\n", (clock()-t)); 
    scanf("%c", &ch);

    return (0); 
}


//获得prefix数组
int* GetPrefixValue(char* strPattern, int iPatternLen)
{
	int i, j;
	/* i runs through the string, j counts the hits*/
	int* prefix = (int*)malloc(iPatternLen*sizeof(int));

	i = 1;
	j = 0;

	prefix[0] = 0;

	while(i<iPatternLen) 
	{
		if(strPattern[i] == strPattern[j])
		{
			prefix[i] = ++j;
        }
		else
		{
			j = 0;
			prefix[i] = j; 
        }
		i++;
    }

	return (prefix);
} 

//返回target串在pattern中第一次匹配的index
int KMPStringMatch(char* strPattern, int iPatternLen, char* strTarget, int iTargetLen, int* prefix) 
{
	int i = 0;
	int j = 0;

	while(i<iPatternLen && j<iTargetLen)
	{
		if(j==0 || strPattern[i]==strTarget[j]) 
		{
			i++;
			j++;
        } 
        else 
        {
			j = prefix[j];
         }
     }

	free(prefix);

	if(j==iTargetLen)
	{
		return i-j;
     }
	else
	{
		return -1;
    } 
}

int KMP(char* strPattern, char* strTarget)
{
	int* prefix = GetPrefixValue(strPattern, strlen(strPattern));
	int index = KMPStringMatch(strPattern, strlen(strPattern), strTarget, strlen(strTarget), prefix);
	return index;
}

//在文本中查找target串出现的位置
int SearchInTxtFile(char* fileName, char* strTarget)
{
	FILE* hFile = fopen(fileName, "r");
	char str[1024];
	int count = 0;
	while(fgets(str, 1024, hFile))
	{
		if(KMP(str, strTarget)!=-1)
		{
			count++;
		} 
	}
	
	fclose(hFile);
	hFile=NULL;

	return (count);
}