day 10a complete

first time using a stack, can recommend

day10/day 10a/stack.go

@@ -0,0 +1,39 @@
+package main
+
+type Stack struct {
+	head *StackNode
+}
+
+func (s *Stack) Push(item byte) {
+	if s.head == nil {
+		s.head = &StackNode{
+			char: item,
+			next: nil,
+		}
+	} else {
+		new := StackNode{
+			char: item,
+			next: s.head,
+		}
+		s.head = &new
+	}
+}
+
+func (s *Stack) Pop() byte {
+	node := s.Peek()
+	s.head = node.next
+	return node.char
+}
+
+func (s *Stack) Peek() (node *StackNode) {
+	node = s.head
+	if node == nil {
+		node = &StackNode{}
+	}
+	return
+}
+
+type StackNode struct {
+	char byte
+	next *StackNode
+}