Data update

Task/Goldbachs-comet/Go/goldbachs-comet.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+var primes []bool
+
+func initialisePrimes(limit int) {
+	primes = make([]bool, limit)
+	for i := 2; i < limit; i++ {
+		primes[i] = true
+	}
+
+	sqrtLimit := int(math.Sqrt(float64(limit)))
+	for n := 2; n < sqrtLimit; n++ {
+		if primes[n] {
+			for k := n * n; k < limit; k += n {
+				primes[k] = false
+			}
+		}
+	}
+}
+
+func goldbachFunction(number int) (int, error) {
+	if number <= 2 || number%2 == 1 {
+		return 0, fmt.Errorf("argument must be even and greater than 2: %d", number)
+	}
+
+	result := 0
+	for i := 1; i <= number/2; i++ {
+		if primes[i] && primes[number-i] {
+			result++
+		}
+	}
+	return result, nil
+}
+
+func main() {
+	initialisePrimes(2000000)
+
+	fmt.Println("The first 100 Goldbach numbers:")
+	for n := 2; n < 102; n++ {
+		value, err := goldbachFunction(2 * n)
+		if err != nil {
+			fmt.Printf("Error: %v\n", err)
+			continue
+		}
+		fmt.Printf("%3d", value)
+		if n%10 == 1 {
+			fmt.Println()
+		}
+	}
+
+	fmt.Println("\nThe 1,000,000th Goldbach number =", func() string {
+		value, err := goldbachFunction(1000000)
+		if err != nil {
+			return fmt.Sprintf("Error: %v", err)
+		}
+		return fmt.Sprintf("%d", value)
+	}())
+}