PHP Program to Fibonacci with Memo with Explanation
PHP
Medium
PHP Functions
39 views
1 min read
79 words
This problem helps you practice core PHP fundamentals in a practical way. It builds intuition around fib, one, fibonacci. Let’s break it down step by step so you can implement it confidently.
Problem Statement
Compute fib(n) with memoization (fib(0)=0, fib(1)=1).
Input Format
One integer n.
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;
$n=intval($inputText);
$memo=[0=>0,1=>1];
function fib($n,&$memo){
if(isset($memo[$n])) return $memo[$n];
$memo[$n]=fib($n-1,$memo)+fib($n-2,$memo);
return $memo[$n];
}
echo fib($n,$memo);
?>
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
Compute fib(n) with memoization (fib(0)=0, fib(1)=1).
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;
$n=intval($inputText);
$memo=[0=>0,1=>1];
function fib($n,&$memo){
if(isset($memo[$n])) return $memo[$n];
$memo[$n]=fib($n-1,$memo)+fib($n-2,$memo);
return $memo[$n];
}
echo fib($n,$memo);
?>
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