Golang | Stack

stack.go

package main

type node struct {
	value interface{}
	next  *node
}

type Stack interface {
	Size() int
	IsEmpty() bool
	Peek() interface{}
	Pop()
	Push(v interface{})
}

type stack struct {
	head *node
	size int
}

func NewStack() Stack {
	return &stack{
		head: nil,
		size: 0,
	}
}

func (st *stack) IsEmpty() bool {
	return st.size == 0
}

func (st *stack) Peek() interface{} {
	if st.head == nil {
		return nil
	}
	return st.head.value
}

func (st *stack) Pop() {
	if st.head != nil {
		top := st.head
		st.head = st.head.next
		st.size--
		// make it GC colltable
		top.next = nil
		top.value = nil
	}
}

func (st *stack) Push(v interface{}) {
	nn := &node{
		value: v,
		next:  nil,
	}
	nn.next = st.head
	st.head = nn
	st.size++
}

func (st *stack) Size() int {
	return st.size
}