Solved exercises 1 to 3

problems_1_to_3.go

@@ -0,0 +1,89 @@
+package euler
+
+// SumMultiples finds the sum of all the multiples of 3 or 5 below 1000
+func SumMultiples() int {
+	result := 0
+
+	for i := range [1000]int{} {
+		if i%3 == 0 || i%5 == 0 {
+			result += i
+		}
+	}
+
+	return result
+}
+
+// EvenFibonacci finds the sum of the even-valued terms of a Fibonacci sequence,
+// considering only the terms whose values do not exceed max
+func EvenFibonacci(max int) int {
+	result := 0
+	first, second := 0, 1
+
+	for second <= max {
+		first, second = second, first+second
+
+		if second%2 == 0 {
+			result += second
+		}
+	}
+
+	return result
+}
+
+// FindLargestPrimeFactor finds the largest prime factor of the number x
+func FindLargestPrimeFactor(x int) int {
+
+	isPrime := func(n int) bool {
+
+		// Check if n=1 or n=0
+		if n <= 1 {
+			return false
+		}
+
+		// Check if n=2 or n=3
+		if n == 2 || n == 3 {
+			return true
+		}
+
+		// Check whether n is divisible by 2 or 3
+		if n%2 == 0 || n%3 == 0 {
+			return false
+		}
+
+		// Check from 5 to square root of n
+		// Iterate i by (i+6)
+		for i := 5; i*i <= n; i = i + 6 {
+			if n%i == 0 || n%(i+2) == 0 {
+				return false
+			}
+		}
+
+		return true
+	}
+
+	if x == 2 || x == 3 {
+		return x
+	}
+
+	for x%2 == 0 {
+		x /= 2
+	}
+
+	for x%3 == 0 {
+		x /= 3
+	}
+
+	largest := 0
+	for i := 5; i <= x; i = i + 1 {
+		if x%i == 0 {
+			for x%i == 0 {
+				x /= i
+			}
+
+			if isPrime(i) {
+				largest = i
+			}
+		}
+	}
+	return largest
+}

problems_1_to_3_test.go

@@ -0,0 +1,19 @@
+package euler
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestSumMultiples(t *testing.T) {
+	fmt.Println(SumMultiples())
+}
+
+func TestEvenFibonacci(t *testing.T) {
+	fmt.Println(EvenFibonacci(4_000_000))
+}
+
+func TestFindLargestPrimeFactor(t *testing.T) {
+	fmt.Println(FindLargestPrimeFactor(13195))
+	fmt.Println(FindLargestPrimeFactor(600851475143))
+}