输入一行文字，找出其中大写字母、小写字母、空格、数字及其他字符各有多少。请路过的高手帮我看看，谢谢
#include"stdio.h"
#include"string.h"
int main()
{
    int upper=0,lower=0,space=0,digit=0,other=0,i=0;

    char *p,s[20];
    printf("input string:");

    while(  (s[i]=getchar())!='\n')i++;
    p=s;
    while(*p!='\n')

    {
        if(  ('A'<=*p)&&(*p<='Z')  )
            ++upper;
        else if( ('a'<='*p')&&(*p<='z')  )
            ++lower;
    else if( *p=='')
        ++space;
        else if( (*p<='9')&&(*p>='0') )
            ++digit;
        else
            ++other;
        p++;
    }
    printf("upper case:%d lower case :%d",upper,lower);
    printf(" digit:%d other:%d\n",digit,other);
    return 0;

}

Compiling...
1.cpp
F:\test\88\1.cpp(20) : error C2137: empty character constant
执行 cl.exe 时出错.

谢谢，hjywyj