- implemented linke list stack - minor changes on other libs - tests included

stacks/linkedliststack/linkedliststack.go

@@ -0,0 +1,92 @@
+/*
+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 linked list.
+// Used by red-black tree during in-order traversal.
+// Structure is not thread safe.
+// References: http://en.wikipedia.org/wiki/Stack_%28abstract_data_type%29
+
+package linkedliststack
+
+import (
+	"fmt"
+)
+
+type Stack struct {
+	top  *element
+	size int
+}
+
+type element struct {
+	value interface{}
+	next  *element
+}
+
+// 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.top = &element{value, stack.top}
+	stack.size += 1
+}
+
+// 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) {
+	if stack.size > 0 {
+		value, stack.top = stack.top.value, stack.top.next
+		stack.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) {
+	if stack.size > 0 {
+		return stack.top.value, true
+	}
+	return nil, false
+}
+
+func (stack *Stack) Empty() bool {
+	return stack.size == 0
+}
+
+func (stack *Stack) Size() int {
+	return stack.size
+}
+
+func (stack *Stack) String() string {
+	str := "RedBlackTree\n"
+	element := stack.top
+	elementsValues := []string{}
+	for element != nil {
+		elementsValues = append(elementsValues, fmt.Sprintf("%v ", element.value))
+		element = element.next
+	}
+	for i, j := 0, len(elementsValues)-1; i < j; i, j = i+1, j-1 {
+		elementsValues[i], elementsValues[j] = elementsValues[j], elementsValues[i]
+	}
+	str += fmt.Sprintf("#v", elementsValues)
+	return str
+}

stacks/linkedliststack/linkedliststack_test.go

@@ -0,0 +1,72 @@
+/*
+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 linkedliststack
+
+import (
+	"testing"
+)
+
+func TestLinkedListStack(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)
+	}
+
+}

trees/redblacktree/redblacktree.go

@@ -20,6 +20,7 @@ with this distribution for more information.
 // Used by TreeSet and TreeMap.
 // Structure is not thread safe.
 // References: http://en.wikipedia.org/wiki/Red%E2%80%93black_tree
+
 package redblacktree
 
 import (
@@ -103,7 +104,7 @@ func (tree *Tree) Put(key interface{}, value interface{}) {
 // Searches the node in the tree by key and returns its value or nil if key is not found in tree.
 // Second return parameter is true if key was found, otherwise false.
 // Key should adhere to the comparator's type assertion, otherwise method panics.
-func (tree *Tree) Get(key interface{}) (interface{}, bool) {
+func (tree *Tree) Get(key interface{}) (value interface{}, found bool) {
 	node := tree.lookup(key)
 	if node != nil {
 		return node.value, true
@@ -144,8 +145,8 @@ func (tree *Tree) Remove(key interface{}) {
 }
 
 // Returns true if tree does not contain any nodes
-func (tree *Tree) IsEmpty() bool {
+func (tree *Tree) Empty() bool {
-	return tree.root == nil
+	return tree.size == 0
 }
 
 // Returns number of nodes in the tree.
@@ -155,7 +156,7 @@ func (tree *Tree) Size() int {
 
 func (tree *Tree) String() string {
 	str := "RedBlackTree\n"
-	if !tree.IsEmpty() {
+	if !tree.Empty() {
 		output(tree.root, "", true, &str)
 	}
 	return str