只ac一半，我不理解，不用string头文件

解题思路:
遍历字符串
注意事项:
判断字符串结尾
参考代码:

#include <stdio.h>

int main() {

char a[10010];

gets(a);

int s = 0, b = 0, c = 0, d = 0;

for (int i = 0; a[i] != '\0'; i++) {

if (a[i] >= 'a' && a[i] <= 'z' || a[i] >= 'A' && a[i] <= 'Z')

s++;

else if (a[i] == ' ')

b++;

else if (a[i] >= '1' && a[i] <= '9')

c++;

else

d++;

}

printf("%d\n%d\n%d\n%d", s, b, c, d);

return 0;

}