array stack (with tests and benchmarks - kinda slow in comparison to the linked list stack)

README.md

@@ -4,4 +4,6 @@
 
 Go Data Structures
 
+## Testing and Benchmarking
 
+`go test -v -bench . -benchmem  -benchtime 1s ./...`

stacks/arraystack/arraystack.go

@@ -0,0 +1,90 @@
+/*
+Copyright (c) Emir Pasic, All rights reserved.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 3.0 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library. See the file LICENSE included
+with this distribution for more information.
+*/
+
+// Implementation of stack using a slice.
+// Use LinkedListStack rather than this Arraystack, because LinkedListStack is a lot faster more memory efficient.
+// Structure is not thread safe.
+// References: http://en.wikipedia.org/wiki/Stack_%28abstract_data_type%29
+
+package arraystack
+
+import (
+	"fmt"
+	"github.com/emirpasic/gods/stacks"
+	"strings"
+)
+
+func assertInterfaceImplementation() {
+	var _ stacks.Interface = (*Stack)(nil)
+}
+
+type Stack struct {
+	items []interface{}
+}
+
+// Instantiates a new empty stack
+func New() *Stack {
+	return &Stack{}
+}
+
+// Pushes a value onto the top of the stack
+func (stack *Stack) Push(value interface{}) {
+	stack.items = append(stack.items, value)
+}
+
+// Pops (removes) top element on stack and returns it, or nil if stack is empty.
+// Second return parameter is true, unless the stack was empty and there was nothing to pop.
+func (stack *Stack) Pop() (value interface{}, ok bool) {
+	size := len(stack.items)
+	if size > 0 {
+		value = stack.items[size-1]
+		stack.items = append([]interface{}(nil), stack.items[:size-1]...)
+		return value, true
+	}
+	return nil, false
+}
+
+// Returns top element on the stack without removing it, or nil if stack is empty.
+// Second return parameter is true, unless the stack was empty and there was nothing to peek.
+func (stack *Stack) Peek() (value interface{}, ok bool) {
+	size := len(stack.items)
+	if size > 0 {
+		return stack.items[size-1], true
+	}
+	return nil, false
+}
+
+// Returns true if stack does not contain any elements.
+func (stack *Stack) Empty() bool {
+	return len(stack.items) == 0
+}
+
+// Returns number of elements within the stack.
+func (stack *Stack) Size() int {
+	return len(stack.items)
+}
+
+func (stack *Stack) String() string {
+	str := "ArrayStack\n"
+	values := []string{}
+	for _, value := range stack.items {
+		values = append(values, fmt.Sprintf("%v", value))
+	}
+	str += strings.Join(values, ", ")
+	return str
+}

stacks/arraystack/arraystack_test.go

@@ -0,0 +1,88 @@
+/*
+Copyright (c) Emir Pasic, All rights reserved.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 3.0 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library. See the file LICENSE included
+with this distribution for more information.
+*/
+
+package arraystack
+
+import (
+	"testing"
+)
+
+func TestArrayStack(t *testing.T) {
+
+	stack := New()
+
+	if actualValue := stack.Empty(); actualValue != true {
+		t.Errorf("Got %v expected %v", actualValue, true)
+	}
+
+	// insertions
+	stack.Push(1)
+	stack.Push(2)
+	stack.Push(3)
+
+	if actualValue := stack.Empty(); actualValue != false {
+		t.Errorf("Got %v expected %v", actualValue, false)
+	}
+
+	if actualValue := stack.Size(); actualValue != 3 {
+		t.Errorf("Got %v expected %v", actualValue, 3)
+	}
+
+	if actualValue, ok := stack.Peek(); actualValue != 3 || !ok {
+		t.Errorf("Got %v expected %v", actualValue, 3)
+	}
+
+	stack.Pop()
+
+	if actualValue, ok := stack.Peek(); actualValue != 2 || !ok {
+		t.Errorf("Got %v expected %v", actualValue, 2)
+	}
+
+	if actualValue, ok := stack.Pop(); actualValue != 2 || !ok {
+		t.Errorf("Got %v expected %v", actualValue, 2)
+	}
+
+	if actualValue, ok := stack.Pop(); actualValue != 1 || !ok {
+		t.Errorf("Got %v expected %v", actualValue, 1)
+	}
+
+	if actualValue, ok := stack.Pop(); actualValue != nil || ok {
+		t.Errorf("Got %v expected %v", actualValue, nil)
+	}
+
+	if actualValue := stack.Empty(); actualValue != true {
+		t.Errorf("Got %v expected %v", actualValue, true)
+	}
+
+}
+
+func BenchmarkArrayStack(b *testing.B) {
+	// Slow in comparison to the LinkedListStack
+	// BenchmarkArrayStack         50  31760994 ns/op  8540863 B/op  2010 allocs/op
+	// BenchmarkLinkedListStack  5000    390812 ns/op    40016 B/op  2001 allocs/op
+	for i := 0; i < b.N; i++ {
+		stack := New()
+		for n := 0; n < 1000; n++ {
+			stack.Push(i)
+		}
+		for !stack.Empty() {
+			stack.Pop()
+		}
+	}
+
+}

stacks/linkedliststack/linkedliststack_test.go

@@ -70,3 +70,18 @@ func TestLinkedListStack(t *testing.T) {
 	}
 
 }
+
+func BenchmarkLinkedListStack(b *testing.B) {
+	// Faster in comparison to the ArrayStack
+	// BenchmarkArrayStack         50  31760994 ns/op  8540863 B/op  2010 allocs/op
+	// BenchmarkLinkedListStack  5000    390812 ns/op    40016 B/op  2001 allocs/op
+	for i := 0; i < b.N; i++ {
+		stack := New()
+		for n := 0; n < 1000; n++ {
+			stack.Push(i)
+		}
+		for !stack.Empty() {
+			stack.Pop()
+		}
+	}
+}