PHP Program to Inventory Item with Explanation
PHP
Medium
PHP OOP Basics
46 views
1 min read
97 words
This problem helps you practice core PHP fundamentals in a practical way. It builds intuition around qty, item, line. Let’s break it down step by step so you can implement it confidently.
Problem Statement
Create Item with qty. Commands: ADD x, SELL x (cannot go below 0). Print final qty.
Input Format
First line q. Next q lines.
Output Format
One integer qty.
Constraints
q
Code Solution
This explanation is written for learning purposes and to help beginners understand the concept clearly.
<?php
class Item{
private $qty=0;
function add($x){ $this->qty += $x; }
function sell($x){ if($this->qty >= $x) $this->qty -= $x; }
function qty(){ return $this->qty; }
}
$inputLines=preg_split('/\\R/', rtrim(stream_get_contents(STDIN)));
if(!$inputLines || trim($inputLines[0])==='') exit;
$q=intval($inputLines[0]);
$item=new Item();
for($i=1;$i<=$q;$i++){
$tokens=preg_split('/\\s+/', trim($inputLines[$i] ?? ''), 2);
$cmd=$tokens[0] ?? '';
$x=intval($tokens[1] ?? 0);
if($cmd==='ADD') $item->add($x);
elseif($cmd==='SELL') $item->sell($x);
}
echo $item->qty();
?>
Output Example
Input:
5
ADD 10
SELL 3
SELL 20
ADD 5
SELL 2
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
Create Item with qty. Commands: ADD x, SELL x (cannot go below 0). Print final qty.
Input / Output
Input
First line q. Next q lines.
Examples
Input:
5
ADD 10
SELL 3
SELL 20
ADD 5
SELL 2
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 Item{
private $qty=0;
function add($x){ $this->qty += $x; }
function sell($x){ if($this->qty >= $x) $this->qty -= $x; }
function qty(){ return $this->qty; }
}
$inputLines=preg_split('/\\R/', rtrim(stream_get_contents(STDIN)));
if(!$inputLines || trim($inputLines[0])==='') exit;
$q=intval($inputLines[0]);
$item=new Item();
for($i=1;$i<=$q;$i++){
$tokens=preg_split('/\\s+/', trim($inputLines[$i] ?? ''), 2);
$cmd=$tokens[0] ?? '';
$x=intval($tokens[1] ?? 0);
if($cmd==='ADD') $item->add($x);
elseif($cmd==='SELL') $item->sell($x);
}
echo $item->qty();
?>
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