PHP Program to Task Manager (Priority Queue) with Explanation
PHP
Hard
PHP OOP Basics
31 views
1 min read
114 words
This problem helps you practice core PHP fundamentals in a practical way. It builds intuition around priority queue, pop, task. Let’s break it down step by step so you can implement it confidently.
Problem Statement
Commands: ADD name p, POP. POP removes and prints the task with highest priority; if tie, the one added earlier. If empty, print EMPTY.
Input Format
First line q. Next q lines.
Output Format
Outputs for POP.
Constraints
q
Code Solution
This explanation is written for learning purposes and to help beginners understand the concept clearly.
<?php
class TaskManager{
private $queue;
private $order=0;
function __construct(){
$this->queue=new SplPriorityQueue();
$this->queue->setExtractFlags(SplPriorityQueue::EXTR_DATA);
}
function addTask($name,$priority){
$this->queue->insert($name, [$priority, -$this->order]);
$this->order++;
}
function popTask(){
if($this->queue->isEmpty()) return null;
return $this->queue->extract();
}
}
$inputLines=preg_split('/\\R/', rtrim(stream_get_contents(STDIN)));
if(!$inputLines || trim($inputLines[0])==='') exit;
$q=intval($inputLines[0]);
$tasks=new TaskManager();
$output=[];
for($lineNo=1;$lineNo<=$q;$lineNo++){
$tokens=preg_split('/\\s+/', trim($inputLines[$lineNo] ?? ''));
$cmd=$tokens[0] ?? '';
if($cmd==='ADD'){
$tasks->addTask($tokens[1] ?? '', intval($tokens[2] ?? 0));
}else{
$name=$tasks->popTask();
$output[] = ($name===null) ? 'EMPTY' : $name;
}
}
echo implode(PHP_EOL,$output);
?>
Output Example
Input:
7
POP
ADD clean 2
ADD build 5
ADD test 5
POP
POP
POP
Output:
EMPTY
build
test
clean
Common Mistakes
- Misreading input/output format.
- Not handling constraints and edge cases.
- Off-by-one errors in loops.
- Forgetting to reset variables between test cases (if any).
Solution Guide
Problem
Commands: ADD name p, POP. POP removes and prints the task with highest priority; if tie, the one added earlier. If empty, print EMPTY.
Input / Output
Input
First line q. Next q lines.
Examples
Input:
7
POP
ADD clean 2
ADD build 5
ADD test 5
POP
POP
POP
Output:
EMPTY
build
test
clean
Details
Common Mistakes
- Misreading input/output format.
- Not handling constraints and edge cases.
- Off-by-one errors in loops.
- Forgetting to reset variables between test cases (if any).
Official Solution
<?php
class TaskManager{
private $queue;
private $order=0;
function __construct(){
$this->queue=new SplPriorityQueue();
$this->queue->setExtractFlags(SplPriorityQueue::EXTR_DATA);
}
function addTask($name,$priority){
$this->queue->insert($name, [$priority, -$this->order]);
$this->order++;
}
function popTask(){
if($this->queue->isEmpty()) return null;
return $this->queue->extract();
}
}
$inputLines=preg_split('/\\R/', rtrim(stream_get_contents(STDIN)));
if(!$inputLines || trim($inputLines[0])==='') exit;
$q=intval($inputLines[0]);
$tasks=new TaskManager();
$output=[];
for($lineNo=1;$lineNo<=$q;$lineNo++){
$tokens=preg_split('/\\s+/', trim($inputLines[$lineNo] ?? ''));
$cmd=$tokens[0] ?? '';
if($cmd==='ADD'){
$tasks->addTask($tokens[1] ?? '', intval($tokens[2] ?? 0));
}else{
$name=$tasks->popTask();
$output[] = ($name===null) ? 'EMPTY' : $name;
}
}
echo implode(PHP_EOL,$output);
?>
Solutions (0)
No solutions submitted yet. Be the first!
