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Binary Tree Breadth-First Search (BFS) Level Order Traversals in Go (GoLang).
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package binarytree | |
// Tree is a binary tree. | |
type Tree struct { | |
Root *Node | |
} | |
// Node is a binary tree node. | |
type Node struct { | |
Val int | |
Left *Node | |
Right *Node | |
} | |
// LevelOrder uses Breadth-First Search (BFS) with queues | |
// to return the Level Order traversal of the tree nodes. | |
func LevelOrder(t *Tree) [][]int { | |
sol := make([][]int, 0) | |
if t == nil || t.Root == nil { | |
return sol | |
} | |
root := t.Root | |
sol = append(sol, []int{root.Val}) | |
queue := NewQueue() | |
queue.Enqueue(root) | |
for !queue.IsEmpty() { | |
level := queue.Size() | |
vals := make([]int, 0) | |
for i := 0; i < level; i++ { | |
current := queue.Dequeue() | |
childrenVals := current.ChildrenVals() | |
vals = append(vals, childrenVals...) | |
queue.EnqueueChildren(current) | |
} | |
if len(vals) != 0 { | |
sol = append(sol, vals) | |
} | |
} | |
return sol | |
} | |
// ChildrenVals returns the children values in a slice. | |
func (n *Node) ChildrenVals() []int { | |
vals := make([]int, 0, 2) | |
if n.Left != nil { | |
vals = append(vals, n.Left.Val) | |
} | |
if n.Right != nil { | |
vals = append(vals, n.Right.Val) | |
} | |
return vals | |
} | |
// Queue is a queue of Nodes. | |
type Queue struct { | |
items []*Node | |
} | |
// NewQueue returns a new Queue. | |
func NewQueue() *Queue { | |
return &Queue{ | |
items: make([]*Node, 0), | |
} | |
} | |
// Enqueue enqueues the Node `node` in the Queue. | |
func (q *Queue) Enqueue(node *Node) { | |
q.items = append(q.items, node) | |
} | |
// EnqueueChildren enqueues the children | |
// of Node `node` in the queue. | |
func (q *Queue) EnqueueChildren(node *Node) { | |
if node.Left != nil { | |
q.Enqueue(node.Left) | |
} | |
if node.Right != nil { | |
q.Enqueue(node.Right) | |
} | |
} | |
// Dequeue dequenes the first Node `node` | |
// from the queue and returns it. | |
// It returns nil if the queue is empty. | |
func (q *Queue) Dequeue() *Node { | |
if q.IsEmpty() { | |
return nil | |
} | |
node := q.items[0] | |
q.items = q.items[1:] | |
return node | |
} | |
// Size returns the size of the Queue | |
// (the number of nodes in queue). | |
func (q *Queue) Size() int { | |
return len(q.items) | |
} | |
// IsEmpty returns whether | |
// the Queue is empty (true) or not (false). | |
func (q *Queue) IsEmpty() bool { | |
return q.Size() == 0 | |
} | |
func (q *Queue) Println() { | |
var sb strings.Builder | |
sb.WriteString("[") | |
if !q.IsEmpty() { | |
for _, item := range q.items[:q.Size()-1] { | |
sb.WriteString(fmt.Sprintf("%v ", item.Val)) | |
} | |
sb.WriteString(fmt.Sprintf("%v", q.items[q.Size()-1].Val)) | |
} | |
sb.WriteString("]") | |
fmt.Println(sb.String()) | |
} |
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package binarytree | |
import "fmt" | |
// Here is an example | |
func main() { | |
t := &Tree{ | |
Root: &Node{ | |
Val: 1, | |
Left: &Node{ | |
Val: 2, | |
Left: &Node{ | |
Val: 3, | |
}, | |
Right: &Node{ | |
Val: 4, | |
}, | |
}, | |
Right: &Node{ | |
Val: 5, | |
}, | |
}, | |
} | |
fmt.Println(LevelOrder(t)) // [[1] [2 5] [3 4]] | |
} |
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