From 8cf64f25396d4fe1a6e7119d38ba56403bd006f7 Mon Sep 17 00:00:00 2001
From: Sidtharthan A N <sidthunagarajan@gmail.com>
Date: Fri, 7 Feb 2020 21:39:35 +0530
Subject: [PATCH] ProjectEuler | Update Problem statement of 002 to match
 projecteuler.net (#38101)

* Correct ProjectEuler:002 definition and tests

From projecteuler.net:
By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
Correct: take all f(n) where f(n) <= 4,000,000 and f(n) is even
Incorrect: take all f(n) where n <= 4,000,000 and f(n) is even

* Incorporate PR review suggestios to ProjectEuler 002

Reword the problem statement

Co-Authored-By: Tom <20648924+moT01@users.noreply.github.com>

Co-authored-by: Tom <20648924+moT01@users.noreply.github.com>
---
 ...roblem-2-even-fibonacci-numbers.english.md | 36 +++++++++----------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-2-even-fibonacci-numbers.english.md b/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-2-even-fibonacci-numbers.english.md
index f1c0bdbd34..842f47e177 100644
--- a/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-2-even-fibonacci-numbers.english.md
+++ b/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-2-even-fibonacci-numbers.english.md
@@ -9,7 +9,7 @@ forumTopicId: 301838
 <section id='description'>
 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:
 <div style='text-align: center;'>1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...</div>
-By considering the terms in the Fibonacci sequence that do not exceed the <code>n</code>th term, find the sum of the even-valued terms.
+By considering the terms in the Fibonacci sequence whose values do not exceed <code>n</code>, find the sum of the even-valued terms.
 </section>
 
 ## Instructions
@@ -22,14 +22,16 @@ By considering the terms in the Fibonacci sequence that do not exceed the <code>
 
 ```yml
 tests:
-  - text: <code>fiboEvenSum(10)</code> should return 44.
-    testString: assert.strictEqual(fiboEvenSum(10), 44);
-  - text: <code>fiboEvenSum(18)</code> should return 3382.
-    testString: assert.strictEqual(fiboEvenSum(18), 3382);
-  - text: <code>fiboEvenSum(23)</code> should return 60696.
-    testString: assert.strictEqual(fiboEvenSum(23), 60696);
-  - text: <code>fiboEvenSum(43)</code> should return 350704366.
-    testString: assert.strictEqual(fiboEvenSum(43), 350704366);
+  - text: <code>fiboEvenSum(10)</code> should return 10.
+    testString: assert.strictEqual(fiboEvenSum(10), 10);
+  - text: <code>fiboEvenSum(60)</code> should return 44.
+    testString: assert.strictEqual(fiboEvenSum(60), 44);
+  - text: <code>fiboEvenSum(1000)</code> should return 798.
+    testString: assert.strictEqual(fiboEvenSum(1000), 798);
+  - text: <code>fiboEvenSum(100000)</code> should return 60696.
+    testString: assert.strictEqual(fiboEvenSum(100000), 60696);
+  - text: <code>fiboEvenSum(4000000)</code> should return 4613732.
+    testString: assert.strictEqual(fiboEvenSum(4000000), 4613732);
   - text: Your function should return an <code>even</code> value.
     testString: assert.equal(fiboEvenSum(10) % 2 === 0, true);
 
@@ -66,16 +68,14 @@ const fiboEvenSum = (number) => {
   if (number <= 1) {
     return 0;
   } else {
-      let evenSum = 2, first = 1, second = 2, fibNum; // According to problem description our Fibonacci series starts with 1, 2
-      for (let i = 3; i <= number; i++) {
-        fibNum = first + second;
-        first = second;
-        second = fibNum;
-        if (fibNum % 2 == 0) {
-          evenSum += fibNum;
-        }
+    let evenSum = 0, prevFibNum = 1, fibNum = 2; // According to problem description our Fibonacci series starts with 1, 2
+    for (let i = 2; fibNum <= number; i++) {
+      if (fibNum % 2 == 0) {
+        evenSum += fibNum;
       }
-      return evenSum;
+      [prevFibNum, fibNum] = [fibNum, prevFibNum + fibNum];
+    }
+    return evenSum;
   }
 }
 ```