Solved problem 27

pe26/pe26.go

@@ -1,82 +1,81 @@
 package pe26
 
 import (
-    "fmt"
-    "strconv"
+	"fmt"
+	"strconv"
 )
 
-
 func max(arr []int) int {
-    result := 0
-    for v := range arr {
-        if v > result {
-            result = v
-        }
-    }
-    return result
+	result := 0
+	for v := range arr {
+		if v > result {
+			result = v
+		}
+	}
+	return result
 }
 func get_next_digit(numerator, denominator int) int {
-    if numerator < denominator {
-        numerator *= 10
-    }
-    remainder := numerator % denominator
-    return remainder
+	if numerator < denominator {
+		numerator *= 10
+	}
+	remainder := numerator % denominator
+	return remainder
 }
 
 func calc_digit_repeat(i int, c chan int) {
-    digit_length := map[int]int {
-        0: 0, 1: 0, 2: 0, 3: 0, 4: 0,
-        5: 0, 6: 0, 7: 0, 8: 0, 9: 0,
-    }
-    rem := 1
-    for {
-        rem = get_next_digit(rem, i)
-        if rem == 0 {
-            // no repeats
-            c <- 0
-            break
-        }
-        if digit_length[rem] > 0 {
-            // found a repeat
-            c <- digit_length[rem]
-            break
-        } else {
-            // new digit
-            // increment other non-zero digits
-            for k, v := range digit_length {
-                if v > 0 {
-                    digit_length[k]++
-                }
-            }
-            digit_length[rem]++
-        }
-    }
+	digit_length := map[int]int{
+		0: 0, 1: 0, 2: 0, 3: 0, 4: 0,
+		5: 0, 6: 0, 7: 0, 8: 0, 9: 0,
+	}
+	rem := 1
+	for {
+		rem = get_next_digit(rem, i)
+		if rem == 0 {
+			// no repeats
+			c <- 0
+			break
+		}
+		if digit_length[rem] > 0 {
+			// found a repeat
+			c <- digit_length[rem]
+			break
+		} else {
+			// new digit
+			// increment other non-zero digits
+			for k, v := range digit_length {
+				if v > 0 {
+					digit_length[k]++
+				}
+			}
+			digit_length[rem]++
+		}
+	}
 }
 
-func start_calc_digit_repeat(i int) (chan int) {
-    c := make(chan int)
+func start_calc_digit_repeat(i int) chan int {
+	c := make(chan int)
 
-    go calc_digit_repeat(i, c)
+	go calc_digit_repeat(i, c)
 
-    return c
+	return c
 }
 
 func Solve(args []string) {
-    N, _ := strconv.Atoi(args[0])
+	N, _ := strconv.Atoi(args[0])
 
-    chan_list := make([]chan int, N)
+	chan_list := make([]chan int, N)
 
-    for i := 1; i <= N; i++ {
-        chan_list[i-1] = start_calc_digit_repeat(i)
-    }
+	for i := 1; i <= N; i++ {
+		chan_list[i-1] = start_calc_digit_repeat(i)
+	}
 
-    max, max_idx := 0, 1
-    for i := 0; i < N; i++ {
-        val := <-chan_list[i]
-        if val > max {
-            max = val
-            max_idx = i + 1
-        }
-    }
-    fmt.Println(max_idx)
+	max, max_idx := 0, 1
+	for i := 0; i < N; i++ {
+		val := <-chan_list[i]
+		if val > max {
+			max = val
+			max_idx = i + 1
+		}
+	}
+	fmt.Println(max_idx)
 }

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)
 }