字符过滤

#include <stdio.h>

void filterchar(const char* src, char* dst)
{
	const char* p;
	int ch;
	int flag[0xff] = {0};
	int i;
	if (src == NULL || dst == NULL)
		return ;
	p = src;
	while (ch = *p++)
	{
		if (!flag[ch])
			flag[ch] = ch;
	}
	for (i = 0; i < 0xff; ++i)
	{
		if (flag[i])
			*dst++ = flag[i];
	}
	*dst = 0;
}
int main(void)
{
	char ch;
	int n = 0;
	char arr[100];
	filterchar("abcd544646.sd.,,,",arr);
	puts(arr);
	return 0;
}