如何从文件读取霍夫曼树频率

Question

I have to create a huffman tree whose alphabtes(symbols, i mean "aaabbacaccba" etc.) must be given as Input.txt file at sole argument.

I then have to create the frequency corresponding to each alphabtes. I have problem in createing frequencies. I want something like this: suppose if i have to read this in input.txt: "aabcccadde" . Then my code must print like this:

sym:a, freq:3
sym:b, freq:1
sym:c, freq:3
sym:d, freq:2
sym:e, freq:1

My code for this is working correctly: see below:

   while (c != EOF && c != '\n' && c != '\r') 
   {
    Object1.data[count].symbol = c;
    if(Object1.data[count].symbol =='a')
    {
      save_a++;
    }
    if(Object1.data[count].symbol =='b')
    {
      save_b++;
    }
    if(Object1.data[count].symbol =='c')
    {
      save_c++;
    }
    if(Object1.data[count].symbol =='d')
    {
      save_d++;
    }
    if(Object1.data[count].symbol =='e')
    {
      save_e++;
    }
    count++;
    c = fgetc(input_file);
   }
    cout<< "save_a : "<<save_a <<endl<< "save_b : "<<save_b <<endl<< "save_c: "<<save_c<<endl<< "save_d : "<<save_d <<endl<< "save_e: "<<save_e<<endl;

so the output is:

save_a : 5
save_b : 3
save_c: 2
save_d : 2
save_e: 3  

But the problem is when user again changes the frequency to "pqabbaddqpc". The user here added two more alphabets, where i have only counter to read the count of a,b,c,d and e only. I mean i want to create some dynamic kind of system where the user can enter any alphabets to calculate the frequencies.

Is it possible to do achieve this ?
Any help please ?

Answer 1

Its simple if you map each alphabet according to its integer value to table which maintains its count .

int freq[256];
char c;
while((c=fgetc(fp))!=EOF) {

  freq[(unsigned int)c]++;;

}

Here as there are only 256 possible characters so there is no memory overhead as such and then you can easily extract the character present in input as they will have freq > 0