Improve day 5

day05/common/crane.go

@@ -16,11 +16,15 @@ func (stack *Stack) Push(crate byte) {
   *stack = append(*stack, crate)
 }
 
-func (stack *Stack) Pop() byte {
+func (stack *Stack) Pop() (byte, bool) {
   last := len(*stack) - 1
-  top := (*stack)[last]
+  if last >= 0 {
-  *stack = (*stack)[:last]
+    top := (*stack)[last]
-  return top
+    *stack = (*stack)[:last]
+    return top, true
+  } else {
+    return 0, false
+  }
 }
 
 func (stack *Stack) Peek() byte {

day05/ex1/main.go

@@ -12,7 +12,7 @@ func main() {
 
   for _, movement := range(movements) {
     for i := 0; i < movement.GetN(); i++ {
-      top := stacks[movement.GetStart() - 1].Pop()
+      top, _ := stacks[movement.GetStart() - 1].Pop()
       stacks[movement.GetEnd() - 1].Push(top)
     }
   }

day05/ex2/main.go

@@ -11,12 +11,13 @@ func main() {
   stacks, movements := common.Parse(*bufio.NewScanner(os.Stdin))
 
   for _, movement := range(movements) {
-    top := []byte{}
+    topStack := common.Stack{}
     for i := 0; i < movement.GetN(); i++ {
-      top = append(top, stacks[movement.GetStart() - 1].Pop())
+      top, _ := stacks[movement.GetStart() - 1].Pop()
+      topStack.Push(top)
     }
-    for i := len(top) - 1; i >= 0; i-- {
+    for top, left := topStack.Pop(); left; top, left = topStack.Pop() {
-      stacks[movement.GetEnd() - 1].Push(top[i])
+      stacks[movement.GetEnd() - 1].Push(top)
     }
   }