通过键盘输入一串小写字母(a~z)组成的字符串。请编写一个字符串过滤程序，若字符串中出现多个相同的字符，将非首次出现的字符过滤掉。

不废话，直接上代码。。。

#include<stdio.h>

#include<string.h>

#include<stdlib.h>

#define maxsize 20

void filter(const char*str1, int length, char* str2)

{

bool hash[26] = { 0 };

int i, j;

for (i = 0, j = 0; i < length; i++)

{

if (hash[str1[i] - 'a'] == false)

{

hash[str1[i] - 'a'] = true;

str2[j++] = str1[i];

}

str2[j] = '\0';

}

}

void zip(const char* str1, int length, char* str2)

{

int i, j, k, num;

char buff[20];

for (i = 0, k = 0; i < length; i++)

{

num = 0;

for ( j = i + 1; i < length; ++j)

{

if (str1[i] == str1[j])

num++;

else

break;

}

if (num != 0)

{

memset(buff, 0, sizeof(buff));//将buff 初始化：

_itoa_s(num + 1, buff, 10);

strcpy_s(str2+k,sizeof(str2+k), buff);

k += strlen(buff);

}

str2[k++] = str1[i];

i = i + num + 1;

}

str2[k] = '\0';

}

int main()

{

char str1[] = { "aaebbc" };

char str2[] = { "aabaa" };

char str3[maxsize] = { 0 };

char str4[maxsize] = { 0 };

filter(str1, strlen(str1), str3);

zip(str2, strlen(str2), str4);

puts(str4);

puts(str3);

return 0;

}