PHP Program to Fast Power Mod with Explanation
PHP
Medium
PHP Operators
23 views
1 min read
81 words
This problem helps you practice core PHP fundamentals in a practical way. It builds intuition around mod, one, fast. Let’s break it down step by step so you can implement it confidently.
Problem Statement
Input a b m. Print (a^b) mod m.
Input Format
One line: a b m.
Output Format
One integer.
Constraints
0
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;
[$a,$b,$m]=array_map('intval',preg_split('/\\s+/', $inputText));
$res=1%$m; $base=$a%$m; $e=$b;
while($e>0){
if($e&1) $res=($res*$base)%$m;
$base=($base*$base)%$m;
$e >>= 1;
}
echo $res;
?>
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
Input a b m. Print (a^b) mod m.
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;
[$a,$b,$m]=array_map('intval',preg_split('/\\s+/', $inputText));
$res=1%$m; $base=$a%$m; $e=$b;
while($e>0){
if($e&1) $res=($res*$base)%$m;
$base=($base*$base)%$m;
$e >>= 1;
}
echo $res;
?>
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