如何改进这个问题？？？ - 编程论坛

题目是，读取一个文件夹的字母，然后把每个字母的频率计算出来，还有write space，大小写，总数都得计算。
EX：
Letter Frequencies:
A              10  B              13
C              20  D              0
E              17  F              4
Rest of Letters
Upper Case    50    Lower Case         17        White Space          10
问题是，结果是26个字母都计算了，出来26次。  但是我只想要有字母的次数，没有提到的字母不写出来。。。。怎么改进
做出来的结果如下：（此程序由yyblackyy原创）

程序代码：

#include<iostream>
#include<fstream>
#include<cctype>
#include<iomanip>
#include<cstdlib>
#define Maxpath 80     // The maximum name of the file
using namespace std;
int fre[26];       // The times of each char
const char str[]="abcdefghijklmnopqrstuvwxyz";    //  Alphabet
static int up=0,low=0,wsp=0,total=0;
void frequency(char ch);
void count(char file_name[]);
void print();
int main()
{

    char filename[Maxpath];
    cout<<"Please enter the file_name"<<endl;
    cin.getline (filename,Maxpath);       // get a file name
    count(filename);
    print();
    return 0;
}
//************************************************
void frequency(char ch)
{
    for(int i=0;i<26;i++)
        if(ch==str[i])
        {
            fre[i]++;
            break;
        }
}
//************************************************************
void count(char filename[])
{
    fstream istr;
    char ch,ch2;
    istr.open (filename,ios::in);
    if(istr.fail ())
    {
        cout<<"Can't open!"<<endl;
        exit(1);
    }

    do
    {
        ch=istr.get ();
        if(isspace(ch))        // judge the write space or not
            wsp++;
        else if(isalpha(ch))        // judge the Alphabet or not
        {
            if(isupper(ch))     // judge the upper case
                up++;
            else                 // judge the lower case
                low++;
            ch2=tolower(ch);           // To lower case
            frequency(ch2);
        }
        else
            ;
        total++;
    }while(!istr.eof());
}
//*****************************************************************
void print()
{
int Count=0;
cout<<"Letter Frequencies:"<<endl;
for(int i=0;i<26;i++)
{    if(fre[i]>Count)
    cout<<char(toupper(str[i]))<<setw(36)<<fre[i]<<endl;
cout<<"Rest of Letters"<<endl;
cout<<"Upper Case"<<endl;
cout<<up<<endl;
cout<<"Lower Case"<<endl;
cout<<low<<endl;
cout<<"White Space"<<endl;
cout<<wsp<<endl;
cout<<"Total char"<<endl;
cout<<total<<endl;

}
system("pause");
}