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lctree.go
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lctree.go
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// Package lctree provides primitives to serialize and deserialize leetcode trees
package lctree
import (
"bytes"
"fmt"
"strconv"
"strings"
)
// TreeNode is a node
type TreeNode struct {
Val int
Left *TreeNode
Right *TreeNode
}
// WalkFn is the signature of the function called on each node
// visited by the function WalkDepthFirst
type WalkFn func(n *TreeNode) error
// WalkDepthFirst traverses the tree depth-first.
// fn is called on each visited node
func (t *TreeNode) WalkDepthFirst(fn WalkFn) error {
stack := make([]*TreeNode, 0)
stack = append(stack, t)
for len(stack) > 0 {
last := len(stack) - 1
node := stack[last]
stack = stack[:last]
if err := fn(node); err != nil {
return err
}
if node.Left != nil {
stack = append(stack, node.Left)
}
if node.Right != nil {
stack = append(stack, node.Right)
}
}
return nil
}
// WalkBFFn is the signature of the function called on each node
// by the function WalkBreadthFirst
type WalkBFFn func(n *TreeNode, depth int) error
type walkBFTreeNode struct {
Node *TreeNode
Depth int
}
// WalkBreadthFirst traverses the tree breadth-first.
// fn is called on each visited node
func (t *TreeNode) WalkBreadthFirst(fn WalkBFFn) error {
queue := make([]walkBFTreeNode, 0)
queue = append(queue, walkBFTreeNode{t, 0})
for len(queue) > 0 {
node := queue[0]
queue = queue[1:]
if err := fn(node.Node, node.Depth); err != nil {
return err
}
if node.Node != nil {
queue = append(queue, walkBFTreeNode{node.Node.Left, node.Depth + 1})
queue = append(queue, walkBFTreeNode{node.Node.Right, node.Depth + 1})
}
// if node.Node.Left != nil {
// queue = append(queue, walkBFTreeNode{node.Node.Left, node.Depth + 1})
// }
// if node.Node.Right != nil {
// queue = append(queue, walkBFTreeNode{node.Node.Right, node.Depth + 1})
// }
}
return nil
}
// DOT converts a TreeNode tree into Graphviz DOT
// See: http://www.graphviz.org/documentation/
func (t *TreeNode) DOT() string {
tree := strings.Builder{}
edges := strings.Builder{}
tree.WriteString("digraph {")
edgeStyleInvisible := "[style=invis]"
nodeStyleInvisible := "[label=\"\", width=.1, style=invis]"
fn := func(n *TreeNode, depth int) error {
if depth == 0 {
if n != nil {
tree.WriteString("\ngraph [ordering=\"out\"];")
} else {
return nil
}
}
if n != nil {
v := strconv.Itoa(n.Val)
tree.WriteString("\n")
tree.WriteString(v)
tree.WriteString(";")
if n.Left != nil || n.Right != nil {
for i, leaf := range []*TreeNode{n.Left, n.Right} {
edges.WriteString("\n")
edges.WriteString(v)
edges.WriteString(" -> ")
if leaf != nil {
edges.WriteString(strconv.Itoa(leaf.Val))
} else {
// Add invisible node to keep the tree balanced
// See https://graphviz.gitlab.io/faq/#FaqBalanceTree
node := fmt.Sprintf("%s.%d", v, i)
tree.WriteString("\n")
tree.WriteString(fmt.Sprintf("%s %s;", node, nodeStyleInvisible))
edges.WriteString(fmt.Sprintf("%s %s", node, edgeStyleInvisible))
}
edges.WriteString(";")
}
}
}
return nil
}
t.WalkBreadthFirst(fn)
if edges.Len() > 0 {
tree.WriteString(edges.String())
tree.WriteString("\n")
}
tree.WriteString("}\n")
return tree.String()
}
// Deserialize converts a leetcode serialized tree into a TreeNode tree
func Deserialize(tree string) *TreeNode {
var root, parent *TreeNode
var right bool
if tree == "[]" {
return nil
}
buf := bytes.Buffer{}
queue := make([]*TreeNode, 0)
for _, r := range tree {
switch r {
case ',', ']':
var node *TreeNode
// Get node
s := buf.String()
buf.Reset()
if s != "null" {
v, _ := strconv.Atoi(s)
node = &TreeNode{Val: v}
}
// Set root
if root == nil {
root, parent = node, node
continue
}
// Append none null nodes to the queue
if node != nil {
queue = append(queue, node)
}
// Set Right or left node
if right {
parent.Right = node
parent = queue[0]
queue = queue[1:]
} else {
parent.Left = node
}
// Switch on and off right
right = !right
case '[':
continue
default:
buf.WriteRune(r)
}
}
return root
}
// Serialize converts a TreeNode tree into a leetcode serialized tree
func Serialize(t *TreeNode) string {
if t == nil {
return "[]"
}
tree := make([]string, 0)
fn := func(n *TreeNode, depth int) error {
var v string
if n != nil {
v = strconv.Itoa(n.Val)
} else {
v = "null"
}
tree = append(tree, v)
return nil
}
t.WalkBreadthFirst(fn)
// Remove all trailing null
cut := len(tree)
for i := len(tree) - 1; i > 0; i-- {
if tree[i] == "null" {
cut--
} else {
break
}
}
return fmt.Sprintf("[%s]", strings.Join(tree[:cut], ","))
}