From 570f58f168dc6966b44b9a6a73ba6c27573843c9 Mon Sep 17 00:00:00 2001
From: David Adi Nugroho <davidadi216@gmail.com>
Date: Sat, 9 Oct 2021 14:10:38 +0700
Subject: [PATCH] Add project euler p1 and p2

---
 DIRECTORY.md               |  2 ++
 ProjectEuler/Problem1.php  | 42 ++++++++++++++++++++++++++++++++++++++
 ProjectEuler/Problem2.php  | 36 ++++++++++++++++++++++++++++++++
 tests/ProjectEulerTest.php | 13 ++++++++++++
 4 files changed, 93 insertions(+)
 create mode 100644 ProjectEuler/Problem1.php
 create mode 100644 ProjectEuler/Problem2.php

diff --git a/DIRECTORY.md b/DIRECTORY.md
index d8e6571..95f4db8 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -19,6 +19,8 @@
   * [Perfectsquare](https://github.com/TheAlgorithms/PHP/blob/master/Maths/PerfectSquare.php)
 
 ## Projecteuler
+  * [Problem1](https://github.com/TheAlgorithms/PHP/blob/master/ProjectEuler/Problem1.php)
+  * [Problem2](https://github.com/TheAlgorithms/PHP/blob/master/ProjectEuler/Problem2.php)
   * [Problem5](https://github.com/TheAlgorithms/PHP/blob/master/ProjectEuler/Problem5.php)
   * [Problem7](https://github.com/TheAlgorithms/PHP/blob/master/ProjectEuler/Problem7.php)
   * [Problem9](https://github.com/TheAlgorithms/PHP/blob/master/ProjectEuler/Problem9.php)
diff --git a/ProjectEuler/Problem1.php b/ProjectEuler/Problem1.php
new file mode 100644
index 0000000..edb920e
--- /dev/null
+++ b/ProjectEuler/Problem1.php
@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * Problem:
+ *
+ * If we list all the natural numbers below 10 that are multiples of 3 or 5,
+ * we get 3, 5, 6 and 9. The sum of these multiples is 23.
+ *
+ * Find the sum of all the multiples of 3 or 5 below 1000.
+ *
+ *
+ * Answer:
+ *
+ * 233168
+ *
+ *
+ * @link https://projecteuler.net/problem=1
+ */
+
+function problem1a(): int
+{
+    $maxNumber = 999; // below 1000
+
+    $numbers = range(1, $maxNumber);
+
+    return array_reduce($numbers, function($carry, $number) {
+        $shouldCarry = $number % 3 == 0 || $number % 5 == 0;
+        return $carry += $shouldCarry ? $number : 0;
+    });
+}
+
+function problem1b(): int
+{
+    $maxNumber = 999; // below 1000
+
+    $numbersMultByThree = range(3, $maxNumber, 3);
+    $numbersMultByFive = range(5, $maxNumber, 5);
+
+    $numbers = array_merge($numbersMultByThree, $numbersMultByFive);
+
+    return array_sum(array_unique($numbers));
+}
diff --git a/ProjectEuler/Problem2.php b/ProjectEuler/Problem2.php
new file mode 100644
index 0000000..85d2f7e
--- /dev/null
+++ b/ProjectEuler/Problem2.php
@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * Problem:
+ *
+ * Each new term in the Fibonacci sequence is generated by adding the previous
+ * two terms. By starting with 1 and 2, the first 10 terms will be:
+ *
+ * 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
+ *
+ * By considering the terms in the Fibonacci sequence whose values do not
+ * exceed four million, find the sum of the even-valued terms.
+ *
+ *
+ * Answer:
+ *
+ * 4613732
+ *
+ *
+ * @link https://projecteuler.net/problem=2
+ */
+
+function problem2(): int
+{
+    $maxNumber = 4000000;
+    $currNumber = 1;
+    $nextNumber = 2;
+    $answer = 0;
+
+    while ($currNumber <= $maxNumber) {
+        $answer += $currNumber % 2 == 0 ? $currNumber : 0;
+        [$currNumber, $nextNumber] = [$nextNumber, $currNumber + $nextNumber];
+    }
+
+    return $answer;
+}
diff --git a/tests/ProjectEulerTest.php b/tests/ProjectEulerTest.php
index 61213d0..75d366a 100644
--- a/tests/ProjectEulerTest.php
+++ b/tests/ProjectEulerTest.php
@@ -3,12 +3,25 @@
 use PHPUnit\Framework\TestCase;
 
 require_once __DIR__.'/../vendor/autoload.php';
+require_once __DIR__.'/../ProjectEuler/Problem1.php';
+require_once __DIR__.'/../ProjectEuler/Problem2.php';
 require_once __DIR__.'/../ProjectEuler/Problem5.php';
 require_once __DIR__.'/../ProjectEuler/Problem7.php';
 require_once __DIR__.'/../ProjectEuler/Problem9.php';
 
 class ProjectEulerTest extends TestCase
 {
+    public function testProblem1(): void
+    {
+        $this->assertSame(233168, problem1a());
+        $this->assertSame(233168, problem1b());
+    }
+
+    public function testProblem2(): void
+    {
+        $this->assertSame(4613732, problem2());
+    }
+
     public function testProblem5(): void
     {
         $this->assertSame(232792560, problem5());