字符统计
include<stdio.h>
main()
{int a=0,b=0,c=0;
char ch;
while((ch=getchar())!='?')
{if(ch>='a'&&ch<='z'||ch>='A'&&ch<='Z')
{a++;}
else{if(ch>='0'&&ch<='9')
{b++;}
else{c++;}}}
printf("Letters=%d\n",a);
printf("Digits=%d\n",b);
printf("Others=%d\n",c);}