求输入的字符的个数（字母，数字，空格，其他）

 #include <iostream>
using namespace std;
int main ()
{char c;
 int letters=0,space=0,digit=0,other=0;
 cout<<"enter one line::"<<endl;
 while((c=getchar())!='/n')
 {if (c>='a' && c<='z'||c>='A' && c<='Z')
     letters++;
  else if (c==' ')
     space++;
  else if (c>='0' && c<='9')
     digit++;
  else
     other++;
  }
  cout<<"letter:"<<letters<<", space:"<<space<<", digit:"<<digit<<", other:"<<other<<endl;
  return 0;
  }