PHP Program to Maximum Subarray Sum with Explanation
PHP
Hard
PHP Arrays
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1 min read
87 words
This problem helps you practice core PHP fundamentals in a practical way. It builds intuition around maximum, subarray, sum. Let’s break it down step by step so you can implement it confidently.
Problem Statement
Print the maximum subarray sum (Kadane).
Input Format
First n. Next line n integers.
Output Format
One integer maxSum.
Constraints
n
Code Solution
This explanation is written for learning purposes and to help beginners understand the concept clearly.
<?php
$inputText=trim(stream_get_contents(STDIN));
if($inputText==='') exit;
$tokens=preg_split('/\\s+/', $inputText);
$i=0; $n=intval($tokens[$i++] ?? 0);
$best=null; $cur=0;
for($k=0;$k<$n;$k++){
$v=intval($tokens[$i++] ?? 0);
if($best===null) $best=$v;
$cur=max($v,$cur+$v);
if($cur>$best) $best=$cur;
}
echo ($best===null?0:$best);
?>
Output Example
Input:
9
-2 1 -3 4 -1 2 1 -5 4
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
Print the maximum subarray sum (Kadane).
Input / Output
Input
First n. Next line n integers.
Output
One integer maxSum.
Examples
Input:
9
-2 1 -3 4 -1 2 1 -5 4
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
$inputText=trim(stream_get_contents(STDIN));
if($inputText==='') exit;
$tokens=preg_split('/\\s+/', $inputText);
$i=0; $n=intval($tokens[$i++] ?? 0);
$best=null; $cur=0;
for($k=0;$k<$n;$k++){
$v=intval($tokens[$i++] ?? 0);
if($best===null) $best=$v;
$cur=max($v,$cur+$v);
if($cur>$best) $best=$cur;
}
echo ($best===null?0:$best);
?>
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