How to store values in struct pointer variable tre

Question

I am new in programming and working on c++ (even the concept of problem is same in c, I guess).

I am reading a file as sole arguments which contains alphabtes(symbols in my code) like "aabbacceaad" to calculate frequency. My code calculate frequency correctly.I am sure of that. The problem is that in my code Node *tree pointer variable (which is of type node). I am using it to create tree.But when i try to create tree from the frequency calculated from repeated symbols then this tree pointer variable only remembers the last executed frequency outside the for-loop. Please take care i just have to use pointers not arrays.

I mean suppose i have symbols in input file like this "aabcddeeebbaa". And the expected output for it is this:

0  symbol:a  Freq:4  Left 0  Right 0  Index1
1  symbol:b  Freq:3  Left 0  Right 0  Index2
2  symbol:c  Freq:1  Left 0  Right 0  Index3
3  symbol:d  Freq:2  Left 0  Right 0  Index4
4  symbol:e  Freq:3  Left 0  Right 0  Index-1

But the output of my code is like this:

0  symbol:e  Freq:3  Left:0  Right:0  Next:5 //Last "e" is executed,tree variable forgot a,b,c and d. 
1  symbol:e  Freq:3  Left:0  Right:0  Next:5
2  symbol:e  Freq:3  Left:0  Right:0  Next:5
3  symbol:e  Freq:3  Left:0  Right:0  Next:5
4  symbol:e  Freq:3  Left:0  Right:0  Next:-1

My full c++ code to do so is :

#include <iostream> 
#include <stdlib.h> 
#include <fstream> 
#include <cassert> 
#include <vector>

using namespace std;

class Huffman {
    public: int data_size,
    length;
    Huffman(char * argv);
    ~Huffman() {};
    vector < char > storesym;
    vector < int > storefreq;
    struct Node
    {
        int value;
        int freq, next;
        short flag;
        unsigned char symbol;
        struct Node * left, * right;
    };
    Node * tree;
};
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////       CONSTRUCTOR definition        ////////////////////////////////////////////////////////////////////////////////
Huffman::Huffman(char * argv) 
{
    char c;
    int count = 0;
    int flag[256]; //this flag is to know if the alphabet is already counted or not.If counted that i set it to "1" other wise it is "0".Please see below in my code
    int j = 0;
    FILE * input_file;
    int  *symbolarray;
    symbolarray=new int[30];
    char i, n;
    input_file = fopen(argv, "rb");
    c = fgetc(input_file);
    //////////////////////////////////////////////////////////////////////////////   From here to down i read the alphabbets from file taken as sole argument ///////////////////////////////////////
    while (c != EOF && c != '\n' && c != '\r')
    {
        symbolarray[count] = c;
        count++;
        c = fgetc(input_file);
    }
    fclose(input_file);

    for (i = 0; i < count; i++)
        flag[i] = {0 };
    int fcount1 = 0;
    for (i = 0; i < count; i++)
    {
        if (flag[i] == 0)
        {
            for (j = i; j < count; j++) 
            {
                if (symbolarray[i] == symbolarray[j]&& flag[j] == 0) 
                {
                    fcount1++;
                    flag[j] = 1; //**I am setting flag to 1 those alphabets to 1 so that they will not be counted again on next iteration**
                }
            }
            storesym.push_back(symbolarray[i]);
            storefreq.push_back(fcount1);
        }
        fcount1 = 0;
    }
    cout << endl;
    //////////////////////////////////////////////////////////////////////////  ERROR PRONE PART STARTS NOW  /////////////////////////////////////////////////////

    for (i = 0; i < storesym.size(); i++) 
    {
        tree = new Node;  // the problem is here this tree pointer don't store the values for all alphabets, it just remembers the last executed alphabet after this for loop.
        tree -> left = NULL;
        tree  ->right = NULL;
        tree -> symbol = storesym[i];
        tree  -> freq = storefreq[i];
        tree -> flag = 0;
        tree -> next = i + 1;
        cout<<"check1 : "<<tree -> symbol<<endl;
    } 
    ////////////////////////////////////////////////////////////////////  eror PRONE PART ENDS HERE  ///////////////////////////////////////////////////////////////////////////////////
    cout << "Here is the data read from file" << endl;
    n = storesym.size() - 1;
    for (int i = 0; i < storesym.size(); i++)
    {
        if (n == i)
        {
            tree  -> next = -1;
            cout << i << "  symbol:" << tree  -> symbol << "  Freq:" << tree  ->freq << "  Left:" << tree  -> left << "  Right:" << tree  -> right << "  Next:" << tree  -> next << endl;
            break;
        } else 
        {
            cout << i << "  symbol:" << tree  -> symbol << "  Freq:" << tree -> freq << "  Left:" << tree  -> left << "  Right:" << tree  ->right << "  Next:" << tree  -> next << endl;
        }
    }
}
//////////////////////////////////////////////////////////////////////////////////////////////////////
int main(int argc, char * * argv)
 {
    int freq[256] = {0};
    if (argc < 2) {
        cout << "Ohh.. Sorry , you forgot to provide the Input File please" << endl;
        return (0);
    }
    Huffman Object1(argv[1]);
    return (0);
}

**Please help me how to keep in memory all the "a,b,c,d and e" (Not just last "e") ? I know there is something to be done with pointers only.

Answer 1

This bit

while (c != EOF && c != '\n' && c != '\r')
{
    tree[count].symbol = c;
    count++;
    c = fgetc(input_file);
}

dereferences the uninitialized pointer tree.
This is a big no-no, and means that your program is formally undefined.
You've just been unlucky in that it hasn't crashed.

You're doing it again a bit further down.

Then you allocate in this loop:

for (i = 0; i < storesym.size(); i++) 
{
    tree = new Node;  // the problem is here this tree pointer don't store the values for all alphabets, it just remembers the last executed alphabet after this for loop.
    tree -> left = NULL;
    tree  ->right = NULL;
    tree -> symbol = storesym[i];
    tree  -> freq = storefreq[i];
    tree -> flag = 0;
    tree -> next = i + 1;
    cout<<"check1 : "<<tree -> symbol<<endl;
} 

which repeatedly allocates one Node and points tree at it.
In other words, it's not building a tree, and you need to rewrite it so it actually does.
Whatever course material you're following should have covered trees recently.

The best advice I can give is: start over, read more, and don't write so much code before testing.