Go Stack

stack.go

package main

import "log"

type Node struct {
	val  int
	next *Node
}

type Stack struct {
	top *Node
}

func (s Stack) Peek() *Node {
	return s.top
}

func (s *Stack) Pop() *Node {
	if s.IsEmpty() {
		return nil
	}

	val := s.top
	s.top = s.top.next

	return val
}

func (s *Stack) Push(node *Node) {
	node.next = s.top
	s.top = node
}

func (s Stack) IsEmpty() bool {
	return s.top == nil
}

func main() {
	stack := &Stack{}

	assert(true, stack.IsEmpty())
	assert((*Node)(nil), stack.Peek())
	assert((*Node)(nil), stack.Pop())

	stack.Push(&Node{val: 1})
	stack.Push(&Node{val: 2})
	stack.Push(&Node{val: 3})

	assert(false, stack.IsEmpty())
	assert(3, stack.Peek().val)
	assert(3, stack.Pop().val)
	assert(2, stack.Pop().val)
	assert(1, stack.Pop().val)
	assert(true, stack.IsEmpty())
	assert((*Node)(nil), stack.Pop())
}

func assert(expected, actual interface{}) {
	if expected != actual {
		log.Panicf("%s != %s", expected, actual)
	}
}