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Merge pull request #108 from rubendelblanco/problem8

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feat:add problem 8 from Euler Project
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Brandon Johnson 2023-04-23 22:21:21 -06:00 committed by GitHub
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1
DIRECTORY.md
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@ -42,6 +42,7 @@
* [Problem5](./Maths/ProjectEuler/Problem5.php)
* [Problem6](./Maths/ProjectEuler/Problem6.php)
* [Problem7](./Maths/ProjectEuler/Problem7.php)
* [Problem8](./Maths/ProjectEuler/Problem8.php)
* [Problem9](./Maths/ProjectEuler/Problem9.php)
## Searches

73
Maths/ProjectEuler/Problem8.php Normal file
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@ -0,0 +1,73 @@
<?php
/**
* This function solves the problem 8 of the Project Euler.
*
* Problem description:
*The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.
*73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450
*Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?
*/
/**
* @return int
*/
function problem8(): int
{
$theNumber = "73167176531330624919225119674426574742355349194934" .
"96983520312774506326239578318016984801869478851843" .
"85861560789112949495459501737958331952853208805511" .
"12540698747158523863050715693290963295227443043557" .
"66896648950445244523161731856403098711121722383113" .
"62229893423380308135336276614282806444486645238749" .
"30358907296290491560440772390713810515859307960866" .
"70172427121883998797908792274921901699720888093776" .
"65727333001053367881220235421809751254540594752243" .
"52584907711670556013604839586446706324415722155397" .
"53697817977846174064955149290862569321978468622482" .
"83972241375657056057490261407972968652414535100474" .
"82166370484403199890008895243450658541227588666881" .
"16427171479924442928230863465674813919123162824586" .
"17866458359124566529476545682848912883142607690042" .
"24219022671055626321111109370544217506941658960408" .
"07198403850962455444362981230987879927244284909188" .
"84580156166097919133875499200524063689912560717606" .
"05886116467109405077541002256983155200055935729725" .
"71636269561882670428252483600823257530420752963450";
$greatestProduct = 0;
$substringSize = 13;
for ($i = 0; $i < strlen($theNumber) - $substringSize; $i++) {
$currentSubstring = substr($theNumber,$i,$substringSize);
$currentProduct = 0;
for ($j = 0; $j < strlen ($currentSubstring); $j++) {
$currentProduct = ($currentProduct == 0 ? (int)$currentSubstring[$j] : $currentProduct * (int)$currentSubstring[$j]);
}
$greatestProduct = ($greatestProduct < $currentProduct ? $currentProduct : $greatestProduct);
}
return $greatestProduct;
}

6
tests/Maths/ProjectEulerTest.php
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@ -9,6 +9,7 @@ require_once __DIR__ . '/../../Maths/ProjectEuler/Problem3.php';
require_once __DIR__ . '/../../Maths/ProjectEuler/Problem5.php';
require_once __DIR__ . '/../../Maths/ProjectEuler/Problem6.php';
require_once __DIR__ . '/../../Maths/ProjectEuler/Problem7.php';
require_once __DIR__ . '/../../Maths/ProjectEuler/Problem8.php';
require_once __DIR__ . '/../../Maths/ProjectEuler/Problem9.php';
class ProjectEulerTest extends TestCase
@ -44,6 +45,11 @@ class ProjectEulerTest extends TestCase
$this->assertSame(104743, problem7());
}
public function testProblem8(): void
{
$this->assertSame(23514624000, problem8());
}
public function testProblem9(): void
{
$this->assertSame(31875000, problem9());