code kata 20230805

binary_tree_230804/stack.go

@@ -0,0 +1,39 @@
+package main
+
+import "errors"
+
+type Stack []interface {
+}
+
+func NewStack() Stack {
+	return Stack{}
+}
+
+func (s Stack) IsEmpty() bool {
+	return len(s) == 0
+}
+
+func (s *Stack) Push(item interface{}) error {
+	*s = append(*s, item)
+	return nil
+}
+
+func (s *Stack) Pop() (interface{}, error) {
+	if s.IsEmpty() {
+		return nil, errors.New("stack is empty")
+	}
+	ret := (*s)[len(*s)-1]
+	*s = (*s)[:len(*s)-1]
+	return ret, nil
+}
+
+func (s Stack) Top() interface{} {
+	if s.IsEmpty() {
+		return nil
+	}
+	return s[len(s)-1]
+}
+
+func (s Stack) Len() int {
+	return len(s)
+}