Add go solution for 100_Doors_Problem

JanBerktold · JanBerktold · commit 123b79b5331e · 2015-03-05T22:06:05.000+01:00
diff --git a/100_Doors_Problem/Go/JanBerktold/main.go b/100_Doors_Problem/Go/JanBerktold/main.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"fmt"
+)
+
+func walk() []int32 {
+	// doors are stored as 32 bit integers
+	// so we actually store 32 * 4 = 128 doors, but we can ignore the extra ones
+	doors := make([]int32, 4)
+
+	for every := 1; every <= 100; every++ {
+		for changeDoor := every; changeDoor <= 100; changeDoor += every {
+			position := uint32(changeDoor % 32)
+			doors[int(changeDoor/32)] ^= (1 << position)
+		}
+	}
+
+	return doors
+}
+
+func printDoors(doors []int32) {
+	for i := 0; i < 100; i++ {
+		element := uint32(i / 32)
+		position := uint32(i % 32)
+		if (doors[element]>>position)&0x01 == 1 {
+			fmt.Printf("%d\n", i)
+		}
+	}
+
+}
+
+func main() {
+	doors := walk()
+	printDoors(doors)
+}
diff --git a/100_Doors_Problem/Go/JanBerktold/main_test.go b/100_Doors_Problem/Go/JanBerktold/main_test.go
@@ -0,0 +1,33 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestDoors(t *testing.T) {
+	doors := walk()
+
+	squarePointer := 0
+	perfectSquares := []int{
+		1, 4, 9, 16, 25, 36, 49, 64, 81,
+	}
+
+	for i := 0; i < 100; i++ {
+		element := uint32(i / 32)
+		position := uint32(i % 32)
+		if (doors[element]>>position)&0x01 == 1 {
+			if perfectSquares[squarePointer] != i {
+				t.Fatalf("Door %v is open but should not be.", i)
+			}
+			squarePointer++
+		} else {
+			if len(perfectSquares) > squarePointer && perfectSquares[squarePointer] == i {
+				t.Fatalf("Door %v should have been open.", i)
+			}
+		}
+	}
+
+	if squarePointer <= len(perfectSquares)-1 {
+		t.Fatalf("Door %v should have been open, however it is not.", perfectSquares[squarePointer])
+	}
+}
