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7.4

Using a queue for Huffman code

Asked by Middletown_Tech in C Programming Language, Microsoft Visual C++.Net

Tags: C, C++, huffman code, queue

Hello,

I am working on creating a Huffman Code (tree). I currently read all symbols and frequencies from a file into Nodes, stored in an array of node *'s, then I sort the array based on frequency and push the sorted nodes into a queue. Now when I try to combine the Nodes I receive and error. I pop the first to nodes from queue and have temp vairables for them, I create a new node and combine the frequencies and alpha characters. However when I try to push the new node back into the queue I receive error message: "deque iteration not referencable".
Please tell me how I can fix this, so that I can pop and push to the same queue?
I created another queue and I am able to push the node * to that queue, so I know it is a problem with accessing the same queue I am popping from. Can someone tell me how I can push a node * back into the same queue?

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             // Proj 5 Huffman Code.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>
#include <iomanip>
#include <queue>
#define ARRAYSIZE 26
using namespace std;
struct treeNode
{
	char alpha[ARRAYSIZE];
	float freq;
	int level;
	struct treeNode *leftPtr, *rightPtr, *parent;
};
typedef struct treeNode TreeNode;
typedef TreeNode *TreeNodePtr; 
TreeNodePtr rootPtr = NULL; 
treeNode * node_position[ARRAYSIZE];
FILE *fp;
queue<treeNode*> q;
queue<treeNode*> huff;
void insertSymbols(); //creates leaf nodes and stores in pointer array
void sortArray(struct treeNode * node_position[]); //sort the array of node pointers
void printSortedArray(struct treeNode * node_position[]); //prints symbols and freq. read from symbol.txt file
void enQueue(struct treeNode * node_position[]); //insert nodes into queue
void createHuff();
int _tmain(int argc, _TCHAR* argv[])
{
	insertSymbols();
	sortArray(node_position);
	printSortedArray(node_position);
	//enQueue(node_position);
	createHuff();
	return 0;
}
void sortArray(struct treeNode * node_position[])//sort the array
{
	int pass; //pass counter
	int c; //comparison counter
	treeNode * hold;  //temp locaion to swap elements
	for(pass=0; pass<ARRAYSIZE; pass++)
	{
		for(c=0; c<ARRAYSIZE-1; c++)
		{
			if(node_position[c]->freq>node_position[c+1]->freq)
			{
				hold=node_position[c];
				node_position[c]=node_position[c+1];
				node_position[c+1]=hold;
			}
		}
	}
}
void printSortedArray(struct treeNode * node_position[])
{
	int i;
	for(i=0; i<ARRAYSIZE; i++)
	{
		cout<<"Symbol is:  "<<node_position[i]->alpha<<"\t"<<"Frequency is:  "<<node_position[i]->freq<<endl;
	}
}
void insertSymbols()
{
	int i;
	fp = fopen("N:\\symbol.txt", "r");
	for(i=0; i<ARRAYSIZE; i++)
	{		
		struct treeNode * treePtr;
		treePtr = (struct treeNode *) malloc (sizeof(treeNode));
		fscanf(fp, "%s", &treePtr->alpha);
		fscanf(fp, "%f", &treePtr->freq);
		node_position[i]=treePtr;
	}
}
void enQueue(struct treeNode * node_position[])
{
	int i;
	for(i=0; i<ARRAYSIZE; i++)
	{		
		q.push(node_position[i]);
	}
	return ;
}
void createHuff()
{
	treeNode *temp1, *temp2;
	treeNode *treePtr;
	
	while (!q.empty())
	{
		temp1=q.front();
		q.pop();
		temp2=q.front();
		q.pop();
		
		treePtr = (struct treeNode*) malloc (sizeof(treeNode));
 
		if(rootPtr==NULL)
			rootPtr=treePtr;
 
		temp1->parent=treePtr;
		temp2->parent=treePtr;
		treePtr->leftPtr=temp1;
		treePtr->rightPtr=temp2;
		strcpy(treePtr->alpha, temp1->alpha);
		strcat(treePtr->alpha,temp2->alpha);
		treePtr->freq=temp1->freq+temp2->freq;
		rootPtr=treePtr;
		q.push(treePtr); /*this causes a problem*/
	                      /*huff.push(treePtr); I can successfully push to this queue*/
	}
}

           
         

Attachments:

symbol.txt (233 bytes) (File Type Details)

file that has symbols and frequencies program reads from

20091111-EE-VQP-89 - Hierarchy / EE_QW_3_20080625

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Using a queue for Huffman code

Asked by Middletown_Tech in C Programming Language, Microsoft Visual C++.Net

Tags: C, C++, huffman code, queue

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