scratch @ efe3f18614c0e2e1994d738b5e9bd127df509d6d

M algos/queue_test.go

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                 	is(t, ok, true)

              
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                32
                 	is(t, v, 11)

              
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                33
                 

              
                
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                +	_, ok = q.Pop()

              
                
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                +	is(t, ok, false)

              
                
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                +

              
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                 	// everything works after removing all elements

              
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                 	q.Push(69420)

              
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                 	is(t, q.Peek(), 69420)

              

A algos/stack.go

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                +package algos

              
                
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                +

              
                
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                +type SNode[T any] struct {

              
                
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                +	v    T

              
                
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                +	prev *SNode[T]

              
                
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                +}

              
                
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                +

              
                
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                +type Stack[T any] struct {

              
                
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                +	Len  int

              
                
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                +	head *SNode[T]

              
                
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                +}

              
                
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                +

              
                
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                +func (s *Stack[T]) Push(item T) {

              
                
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                +	node := &SNode[T]{v: item, prev: s.head}

              
                
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                +	s.head = node

              
                
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                +	s.Len++

              
                
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                +}

              
                
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                +

              
                
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                +func (s *Stack[T]) Peek() T {

              
                
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                +	return s.head.v

              
                
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                +}

              
                
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                +

              
                
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                +func (s *Stack[T]) Pop() (val T, ok bool) {

              
                
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                +	if s.Len == 0 {

              
                
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                +		var t T

              
                
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                +		return t, false

              
                
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                +	}

              
                
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                +	res := s.head.v

              
                
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                +	s.head = s.head.prev

              
                
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                +	s.Len--

              
                
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                +	return res, true

              
                
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                +}

              

A algos/stack_test.go

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                +package algos

              
                
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                +

              
                
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                +import "testing"

              
                
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                +

              
                
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                +func TestStack(t *testing.T) {

              
                
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                +	s := Stack[int]{}

              
                
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                +

              
                
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                +	s.Push(5)

              
                
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                +	s.Push(7)

              
                
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                +	s.Push(9)

              
                
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                +

              
                
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                +	v, ok := s.Pop()

              
                
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                +	is(t, ok, true)

              
                
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                +	is(t, v, 9)

              
                
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                +

              
                
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                +	is(t, s.Len, 2)

              
                
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                +

              
                
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                +	s.Push(11)

              
                
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                +

              
                
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                +	v, ok = s.Pop()

              
                
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                +	is(t, ok, true)

              
                
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                +	is(t, v, 11)

              
                
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                +

              
                
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                +	v, ok = s.Pop()

              
                
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                +	is(t, ok, true)

              
                
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                +	is(t, v, 7)

              
                
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                +

              
                
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                +	is(t, s.Peek(), 5)

              
                
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                +

              
                
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                +	v, ok = s.Pop()

              
                
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                +	is(t, ok, true)

              
                
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                +	is(t, v, 5)

              
                
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                +

              
                
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                +	_, ok = s.Pop()

              
                
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                +	is(t, ok, false)

              
                
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                +

              
                
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                +	s.Push(69420)

              
                
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                +	is(t, s.Peek(), 69420)

              
                
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                +

              
                
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                +	v, ok = s.Pop()

              
                
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                +	is(t, ok, true)

              
                
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                +	is(t, v, 69420)

              
                
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                +}