I've got a priority queue of items who, from time to time, returns a different comparison result. Any way to re-sort a priority queue who is storing them?
Example:
#include <cstdlib>
struct Random {
bool operator<(const Random&) const { return !(rand()&1); } };
How to build a FiFO queue without using the STL (done that no problem), get it to dequeue (again, done that no problem). However, to get those extra marks, I need to be able to order it using a priority system.
I've tried ordering the NodeDequeue class that I'll show at the bottom of this post, but I just cannot get it to order appropriately. The closest I have got is everything in order but I lose a Node from the memory completely. So, that's no good.
The most logical idea I have thought of right now is to send the largest number to the back of the queue each time it's iterated, eventually, the largest number will end up at the front.
class PriorityQueue : public Queue {
public:
Node* NodeDequeue(void) {
Node* tmp = front;
Node* seek = tmp->getPrev();
[Code] .....
I'm trying to implement Prim's Algorithm and for that I need to have a decreaseKey method for a priority queue (to update the key value in a priority queue). Can I implement this in the STL Priority Queue?
This is the algorithm I'm following:
for each vertex u in graph G
set key of u to INFINITY
set parent of u to NIL
set key of source vertex to 0
en-queue to priority queue Q all vertices in graph
[Code] .....
how double ended priority queue be used to implement external quick sort?
View 8 Replies View RelatedI know queue but with priority queue i am really amateur. How to implement some functions in priority queue.
template <class T> class PRIORITY_QUEUE {
private:
T *items; // array of queue items
int rear;
int maxSize; // maximum size of queue
[Code] ....
and what does heapify mean???
write a program, pfpq.c, that maintains a priority queue of music tracks (songs) and ratings. The struct is given by:
Code:
struct track
{
char artist[20];
char title[20];
int rating;
};
The program is only designed to demonstrate the concept so get the user to enter a small number of tracks and create a priority queue. (Use an empty string title or an empty string artist to end the program). Print the priority queue as it grows. Your program should initially ask the user if they wish to order the priority queue by rating in ascending order, or by rating in descending order, or if they wish to order the priority queue by artist name. Then build the priority queue accordingly. in the last case, "if they wish to order the priority queue by artist name." which is case 3. How do I sort the priority queue by artist name using in the following code.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pqueue.h"
struct track
{
char artist[20];
char title[20];
int rating;
}
[code]....
i am working on creating a priority queue, i seem to have done the algorithm for inserting from the top correctly but the algorithm for inserting from the bottom doesnt seem to work it just overwrites the existing data.
below is my code :
list is an array and listlength is the size of the array declared as a integer
void inserttop(string task) {
//int head = 0 ;
string temp ;
listlength++ ;
for (int i = 1; i < listlength; i++) {
[Code]...
So i have been banging my head against a wall with this problem for awhile. I have also copy and pasted direct examples from the internet but nothing seems to sort it right.
Node Header
Code:
#ifndef _NODE_H
#define _NODE_H
#include <stdio.h>
class Node {
public:
Node();
Node(int weight, char value, Node* left = NULL, Node* right = NULL);
[Code] ....
On several occasions in my project, I need to sort elements (indeces) based on their linked values. Those values are stored in an array. This means the comparison looks like this:
bool operator()(int i, int j) { return someArray[i] > someArray[j]; }
Because this form returns often but someArray may differ, I wrapped this in a template class:
template<class T>
struct sorter {
std::vector<T>& data;
sorter(std::vector<T>& __d) : data(__d) {}
bool operator()(int i, int j) const { return data[i] > data[j]; }
};
Now, I want to use this in a different way: I want to select the K indeces with the lowest value from someArray attached to it. My idea was to build a priority_queue, push the first K elements and then compare all the next elements to PQ.top(), as such:
INDEX t(0);
for (; t < someLimit; ++t) {
pq.push(t);
if (pq.size() == K) break;
}
for (; t < someLimit; ++t) {
if (someArray[t] < someArray[pq.top()]) { pq.pop(); pq.push(t); }
}
My problem, however, is the definition / initialization of the priority_queue object. My first idea was simply std::priority_queue<INDEX> pq(sorter<VALUE>(someArray));, but calling any function on pq provides the error "expression must have class type" (?) when hovering over pq.
My second guess, std::priority_queue<INDEX, std::vector<INDEX>, sorter<VALUE>(someArray)> pq;, provides the error 'expected a ')'' when hovering over someArray.
What is the correct way to initialize this data structure?
This assignment is about Heap and PQ's to sort out jobs inside a printer. I'm far from finishing the assignment but the most important part isn't working. My issue is that nothing is getting stored inside the array. I keep getting crashes and at this point I'm not sure what to do. I notice that my destructor runs right after my "addJob" Function finishes, which is destroying the memory. Which might be why nothing gets stored inside OR I think my implementation of Heap/PQ is wrong.
Functions inside my test.cpp aren't properly done, they are made just to see if something is stored inside.
1. Check if I created the array correctly [PQtype.cpp / Heap.h/ PQType.h]
2. Am I even using/storing into the array. [Test.cpp "addJob" Function]
3. I'm also new to working with Class Templates.
PQType.h
template<class ItemType>
class PQType {
public:
PQType(int);
PQType(const PQType&); /
[Code] .....
There appears to be some kind of error in by removeMin() function. Inserting items seems to work just fine but attempting to remove any items gives me the error "vector subscript out of range".
Here is my SortedPQ class... Below it you will find the quicksort implementation, in case looking at it is necessary.
template <class Type>
class SortedPQ {
private:
int front;
int rear;
vector<Type> V;
public:
SortedPQ(void) : front(-1), rear(-1), V(0){}
[Code] ....
I've got 2 classes, Store and Transaction and I would like to create a priority queue of objects Transaction as a variable of Store class.
My store.h
#ifndef __STORE_H_INCLUDED__
#define __STORE_H_INCLUDED__
#include <queue>
using namespace std;
#include "Transaction.h"
struct TransactionCompare;
[Code] ....
The error im getting with this set up is
error C2664: 'bool TransactionCompare::operator ()(const Transaction &,const Transaction &)
const' : cannot convert parameter 1 from 'Transaction *' to 'const Transaction &'
I'm trying to use a priority queue sorting in reverse order to take a vector or 2d array. The problem is that I want to sort by the vector/array cell value but keep the reference to the vector/array index of the value. I don't know quite howto keep them both related so when I pop. I can find the corresponding cell.
priority_queue<int, vector<int>, greater<int> > Open;
I have a paradigm in a loop of queues of a vector,if a condition is true,increase sizes of the queue of that particular queue in the loop of queues, if condition is false, the queuesize is left as such in loop of queues. After this operation i need to search the queue sizes of all queues and enqueue in the shortest queue.
I want to do something like the code given below
#include <vector>
#include <queue>
int min_index = 0;
std::vector<std::queue<int> > q
std::size_t size = q.size();
[Code] ....
How to implement this logic?
will q[i].size=q[i].size+5 increase the queuesize by 5 for the ith queue?
Is it possible to write a program such that it will automatically execute the function in queue base on their priority even if user programmed it randomly?
Code:
function1(){ very_important; }
function2(){ important; }
function3(){ less_important; }
int main() { // Programmed by user
function3;
function1;
function2;
//Output: Program will execute function1, 2 and lastly 3.
}
I have created a string array of 5 and I will use that to enter some "tasks", then I also have an integer array of 5 where i can assign priorities to the information in the string
string info[5];
int p[5];
cout<<"Enter info 1"<<endl;
cin>>info[0];
cout<<"Enter priority"<<endl;
cin>>p[0];
etc,
I want to be able to link the priorities that i assign to that string and be able to call the information that has the highest priority. I can only using iostream and string header files so far,
quishing some bugs, and also how to go about squishing these bugs?
#include "stdafx.h"
#include<stdio.h>
#include<malloc.h>
[Code].....
Here are the errors after compiling the program.
I'm the author of a realtime MIDI software called ChordEase which makes use of the MIDI aspects of the multimedia API, specifically MIDI input callbacks. In XP and before, these callbacks originated in the kernel and therefore had realtime priority by definition, but from Vista on, they originate in thread pool threads, and have a priority of zero. This is a problem because at priority zero they can be blocked by the GUI thread, causing serious latency, and I have proved that such blocking occurs.
I have experimented with raising the callback thread priority, using either of the following methods: 1) calling SetThreadPriority within the MIDI input callback function, and then setting a flag so that it isn't done repeatedly, or 2) creating a DLL that catches thread creation via DLL_ATTACH_THREAD in DllMain, and calling SetThreadPriority there. The first method is slightly wasteful since the flag has to be tested for every MIDI input event, but it also has the advantage of only affecting the MIDI input threads, whereas the second method affects all threads in the pool regardless of what they're used for. Neither method appears to cause any harmful effects but they make me nervous*. Other possible methods would include 3) using the thread pool API to raise the priority of the pool (assuming I could gain access to the pool handle somehow), or 4) permanently lowering the priority of the GUI thread, which I'm very reluctant to do because of the risk of unintended consequences.
I'm assuming the MIDI input callbacks are using threads in the default thread pool though I haven't actually proved this. Assuming that's so, are these threads private to my application, or is my application sharing them with other applications? Is there a safer way to achieve the result of increasing the priority of MIDI input callbacks? It's incredibly frustrating that MS would change the behavior of MIDI input callbacks so drastically without even telling anyone, but that's how it goes!
[URL] ....
*See for example theses warnings about changing thread pool priorities : [URL] ....
I'm having a problem with removing an item from a queue. At first in the debugger I got SIGTRAP but I don't get it anymore but the problem still exists. When you try to remove an item from the queue the first nothing happens. Here's the code below compile it and you see what I'm talking about.
Code:
#include <stdio.h>
#include <stdlib.h>
struct Node {
char let;
struct Node *nextNode;
};
[code]....
I have an assignment that needs to display the names of customers to be served according to a sequence. coding to display the names accordingly?
Code:
#include <stdio.h>
#include <stdlib.h>
#define MAXIMUM 20
void create();
[Code].....
This is my output. I have trouble displaying the names of the customers as it outputs null when I try to display my position in queue.
Why is this code not marking that the queue is full.. I'm just including my Add function that verifies if they want to add another number to the queue. The isFull function works fine, have used it on other programs.
template <class T> //Template currSize function
int Queue<T> :: currSize ()
{
return (rear - front + arraylength) % arraylength; //
[Code].....
The output goes all the way down to 1 spot left, lets the user enter the last element. Then it asks if they want to add another.. At this point, when they hit Y, it lets them add it and it says there are 5 spots left!
I've been working on a little project and hit a snag. I'm using nodes for a queue and stack class that were created using an existing list node class. I create an object for a student class and I want to enqueue that object.
int main() {
Queue sLine;
Customer stu;
Queue<Student &>
cLine.enqueue(cust);
}
That's basically the coding of it in main. However when I follow the error which says uninitialized reference member ListNode<Student& info>::data;
#ifndef LISTND_H
#define LISTND_H
template< class T > class List;
template< class NODETYPE >
class ListNode {
friend class List< NODETYPE >;
[Code] .....
What I may have been doing wrong? Trying to work within certain contexts.
Is there any possible way to create an STL queue of arrays? I tried
queue<int[]>q;
It didn't work?
what is the empty state of queue?
View 5 Replies View RelatedWrite a program to simulate a printer queue (priority queue or heap – Bentley article has code) where 3 printers are “fed” by this queue. Each print job has an unchanging priority and higher priority jobs go first (although once started, a job isn't stopped to let a higher one go). For each unit of time, there is a 26% probability that a job will be added to the queue and all jobs take 8 time units to complete. Print job priorities are between 5 and 100. The queue opens 20 time units prior to the start of printing for adding print “jobs”. A print “day” is 1000 time units. The output from your program is:
1) A list of jobs completed with their priorities for each printer
2) A list of jobs not completed (if any).
#include <iostream>
#include <cstdio>
#include <cstring>
[Code].....
while the prog. running compiler say " access violation .. "
this my code ...
solved :just forget to make r=NULL ; rf =NUll ; frontm=NUll; frontf=NULL ;
#include <iostream>
#include<conio>
struct stu{
int id;
float gba ;
char gender ;
stu *next ;
}*r ,*rf ;
stu read()
[code]....