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- adding save color(node) function to guard against nil-nodes

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pull/1/head
Emir Pasic 9 years ago
parent 8e21214018
commit ca8727c91c
1 changed files with 86 additions and 68 deletions
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154
trees/redblacktree/redblacktree.go
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@ -130,7 +130,7 @@ func (tree *Tree) Remove(key interface{}) {
child = node.right
}
if node.color == BLACK {
node.color = child.color
node.color = color(child)
tree.deleteCase1(node)
}
tree.replaceNode(node, child)
@ -146,36 +146,43 @@ func (tree *Tree) IsEmpty() bool {
}
func (tree *Tree) String() string {
str := "RedBlackTree\n"
if !tree.IsEmpty() {
levels := make(map[int][]*Node)
lastLevel := 0
levels[lastLevel] = append(levels[lastLevel], tree.root)
for len(levels[lastLevel]) > 0 {
for _, node := range levels[lastLevel] {
if node.left != nil {
levels[lastLevel+1] = append(levels[lastLevel+1], node.left)
}
if node.right != nil {
levels[lastLevel+1] = append(levels[lastLevel+1], node.right)
}
}
lastLevel += 1
}
str := "tree\n"
for i := 0; i < lastLevel; i++ {
for _, node := range levels[i] {
str += fmt.Sprintf("%s", node)
}
str += "\n"
}
return str
output(tree.root, "", true, &str)
}
return "tree\n"
return str
}
func (node *Node) String() string {
return fmt.Sprintf("(%v)", node.key)
return fmt.Sprintf("%v", node.key)
}
func output(node *Node, prefix string, isTail bool, str *string) {
if node.right != nil {
newPrefix := prefix
if isTail {
newPrefix += "│ "
} else {
newPrefix += " "
}
output(node.right, newPrefix, false, str)
}
*str += prefix
if isTail {
*str += "└── "
} else {
*str += "┌── "
}
*str += node.String() + "\n"
if node.left != nil {
newPrefix := prefix
if isTail {
newPrefix += " "
} else {
newPrefix += "│ "
}
output(node.left, newPrefix, true, str)
}
}
func (tree *Tree) lookup(key interface{}) *Node {
@ -265,18 +272,15 @@ func (tree *Tree) insertCase1(node *Node) {
}
func (tree *Tree) insertCase2(node *Node) {
if node.parent.color == BLACK {
return /* Tree is still valid */
if color(node.parent) == BLACK {
return
}
tree.insertCase3(node)
}
func (tree *Tree) insertCase3(node *Node) {
uncle := node.uncle()
if uncle == nil {
return
}
if uncle.color == RED {
if color(uncle) == RED {
node.parent.color = BLACK
uncle.color = BLACK
node.grandparent().color = RED
@ -287,10 +291,11 @@ func (tree *Tree) insertCase3(node *Node) {
}
func (tree *Tree) insertCase4(node *Node) {
if node == node.parent.right && node.parent == node.grandparent().left {
grandparent := node.grandparent()
if node == node.parent.right && node.parent == grandparent.left {
tree.rotateLeft(node.parent)
node = node.left
} else if node == node.parent.left && node.parent == node.grandparent().right {
} else if node == node.parent.left && node.parent == grandparent.right {
tree.rotateRight(node.parent)
node = node.right
}
@ -299,11 +304,12 @@ func (tree *Tree) insertCase4(node *Node) {
func (tree *Tree) insertCase5(node *Node) {
node.parent.color = BLACK
node.grandparent().color = RED
if node == node.parent.left && node.parent == node.grandparent().left {
tree.rotateRight(node.grandparent())
} else if node == node.parent.right && node.parent == node.grandparent().right {
tree.rotateLeft(node.grandparent())
grandparent := node.grandparent()
grandparent.color = RED
if node == node.parent.left && node.parent == grandparent.left {
tree.rotateRight(grandparent)
} else if node == node.parent.right && node.parent == grandparent.right {
tree.rotateLeft(grandparent)
}
}
@ -326,9 +332,10 @@ func (tree *Tree) deleteCase1(node *Node) {
}
func (tree *Tree) deleteCase2(node *Node) {
if node.sibling().color == RED {
sibling := node.sibling()
if color(sibling) == RED {
node.parent.color = RED
node.sibling().color = BLACK
sibling.color = BLACK
if node == node.parent.left {
tree.rotateLeft(node.parent)
} else {
@ -339,11 +346,12 @@ func (tree *Tree) deleteCase2(node *Node) {
}
func (tree *Tree) deleteCase3(node *Node) {
if node.parent.color == BLACK &&
node.sibling().color == BLACK &&
node.sibling().left.color == BLACK &&
node.sibling().right.color == BLACK {
node.sibling().color = RED
sibling := node.sibling()
if color(node.parent) == BLACK &&
color(sibling) == BLACK &&
color(sibling.left) == BLACK &&
color(sibling.right) == BLACK {
sibling.color = RED
tree.deleteCase1(node.parent)
} else {
tree.deleteCase4(node)
@ -351,11 +359,12 @@ func (tree *Tree) deleteCase3(node *Node) {
}
func (tree *Tree) deleteCase4(node *Node) {
if node.parent.color == RED &&
node.sibling().color == BLACK &&
node.sibling().left.color == BLACK &&
node.sibling().right.color == BLACK {
node.sibling().color = RED
sibling := node.sibling()
if color(node.parent) == RED &&
color(sibling) == BLACK &&
color(sibling.left) == BLACK &&
color(sibling.right) == BLACK {
sibling.color = RED
node.parent.color = BLACK
} else {
tree.deleteCase5(node)
@ -363,32 +372,41 @@ func (tree *Tree) deleteCase4(node *Node) {
}
func (tree *Tree) deleteCase5(node *Node) {
sibling := node.sibling()
if node == node.parent.left &&
node.sibling().color == BLACK &&
node.sibling().left.color == RED &&
node.sibling().right.color == BLACK {
node.sibling().color = RED
node.sibling().left.color = BLACK
tree.rotateRight(node.sibling())
color(sibling) == BLACK &&
color(sibling.left) == RED &&
color(sibling.right) == BLACK {
sibling.color = RED
sibling.left.color = BLACK
tree.rotateRight(sibling)
} else if node == node.parent.right &&
node.sibling().color == BLACK &&
node.sibling().right.color == RED &&
node.sibling().left.color == BLACK {
node.sibling().color = RED
node.sibling().right.color = BLACK
tree.rotateLeft(node.sibling())
color(sibling) == BLACK &&
color(sibling.right) == RED &&
color(sibling.left) == BLACK {
sibling.color = RED
sibling.right.color = BLACK
tree.rotateLeft(sibling)
}
tree.deleteCase6(node)
}
func (tree *Tree) deleteCase6(node *Node) {
node.sibling().color = node.parent.color
sibling := node.sibling()
sibling.color = color(node.parent)
node.parent.color = BLACK
if node == node.parent.left && node.sibling().right.color == RED {
node.sibling().right.color = BLACK
if node == node.parent.left && color(sibling.right) == RED {
sibling.right.color = BLACK
tree.rotateLeft(node.parent)
} else if node.sibling().left.color == RED {
node.sibling().left.color = BLACK
} else if color(sibling.left) == RED {
sibling.left.color = BLACK
tree.rotateRight(node.parent)
}
}
func color(node *Node) Color {
if node == nil {
return BLACK
}
return node.color
}

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