Solved problem 27

pe26/pe26.go

@@ -5,7 +5,6 @@ import (
 	"strconv"
 )
 
-
 func max(arr []int) int {
 	result := 0
 	for v := range arr {
@@ -53,7 +52,7 @@ func calc_digit_repeat(i int, c chan int) {
 	}
 }
 
-func start_calc_digit_repeat(i int) (chan int) {
+func start_calc_digit_repeat(i int) chan int {
 	c := make(chan int)
 
 	go calc_digit_repeat(i, c)

pe27/pe27.go

@@ -0,0 +1,69 @@
+package pe27
+
+import (
+	"fmt"
+	"math"
+)
+
+type Params struct {
+	A int
+	B int
+	N int
+}
+
+func is_prime(x int) bool {
+	if x < 0 {
+		x = -x
+	}
+	if x == 0 || x == 1 {
+		return false
+	}
+	if x == 2 {
+		return true
+	}
+	for i := 2; float64(i) <= math.Sqrt(float64(x)); i++ {
+		if x%i == 0 {
+			return false
+		}
+	}
+	return true
+}
+
+func count_primes(a, b int, c chan Params) {
+	num_primes := 0
+	for n := 0; ; n++ {
+		ans := n*n + a*n + b
+		if !is_prime(ans) {
+			break
+		} else {
+			num_primes++
+		}
+	}
+	c <- Params{a, b, num_primes}
+}
+
+func Solve(_ []string) {
+	c := make(chan Params, 3999999)
+	var a, b int
+	for a = -999; a < 1000; a++ {
+		for b = -1000; b < 1001; b++ {
+			go count_primes(a, b, c)
+		}
+	}
+
+	max_a, max_b, max := 0, 0, 0
+	for i := 0; i < 3999999; i++ {
+		arr := <-c
+		if arr.N > max {
+			max_a = arr.A
+			max_b = arr.B
+			max = arr.N
+		}
+	}
+	fmt.Println("A:", max_a, "B:", max_b, "Num Primes:", max, "A * B:", max_a*max_b)
+	/*
+	   for i := 0; i < 100; i++ {
+	       fmt.Println("i:", i, "is prime:", is_prime(i))
+	   }
+	*/
+}

projecteuler.go

@@ -4,21 +4,26 @@ import (
 	"fmt"
 	"os"
 
-	"shillerben.com/gitlab/shillerben/projecteuler/pe26"
+	"shillerben.com/gitlab/shillerben/projecteuler-go/pe26"
+	"shillerben.com/gitlab/shillerben/projecteuler-go/pe27"
 )
 
 var solve_funcs = map[string]func([]string){
 	"26": pe26.Solve,
+	"27": pe27.Solve,
 }
 
 func main() {
-	if len(os.Args) < 3 {
+	if len(os.Args) < 2 {
 		fmt.Println("usage: projecteuler <problem number> <problem args>")
 		return
 	}
 
 	problem_number := os.Args[1]
-	problem_args := os.Args[2:]
+	var problem_args []string
+	if len(os.Args) > 2 {
+		problem_args = os.Args[2:]
+	}
 
 	solve_funcs[problem_number](problem_args)
 }