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v/examples/binary_search_tree.v

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V

// Binary Search Tree example by @SleepyRoy
struct Empty {}
struct Node[T] {
value T
left Tree[T]
right Tree[T]
}
type Tree[T] = Empty | Node[T]
// return size(number of nodes) of BST
fn (tree Tree[T]) size[T]() int {
return match tree {
Empty { 0 }
Node[T] { 1 + tree.left.size() + tree.right.size() }
}
}
// insert a value to BST
fn (tree Tree[T]) insert[T](x T) Tree[T] {
return match tree {
Empty {
Node[T]{x, tree, tree}
}
Node[T] {
if x == tree.value {
tree
} else if x < tree.value {
Node[T]{
...tree
left: tree.left.insert(x)
}
} else {
Node[T]{
...tree
right: tree.right.insert(x)
}
}
}
}
}
// whether able to find a value in BST
fn (tree Tree[T]) search[T](x T) bool {
return match tree {
Empty {
false
}
Node[T] {
if x == tree.value {
true
} else if x < tree.value {
tree.left.search(x)
} else {
tree.right.search(x)
}
}
}
}
// find the minimal value of a BST
fn (tree Tree[T]) min[T]() T {
return match tree {
Empty {
T(1e9)
}
Node[T] {
if tree.value < tree.left.min() {
tree.value
} else {
tree.left.min()
}
}
}
}
// delete a value in BST (if nonexistant do nothing)
fn (tree Tree[T]) delete[T](x T) Tree[T] {
return match tree {
Empty {
tree
}
Node[T] {
if tree.left !is Empty && tree.right !is Empty {
if x < tree.value {
Node[T]{
...tree
left: tree.left.delete(x)
}
} else if x > tree.value {
Node[T]{
...tree
right: tree.right.delete(x)
}
} else {
Node[T]{
...tree
value: tree.right.min()
right: tree.right.delete(tree.right.min())
}
}
} else if tree.left !is Empty {
if x == tree.value {
tree.left
} else {
Node[T]{
...tree
left: tree.left.delete(x)
}
}
} else {
if x == tree.value {
tree.right
} else {
Node[T]{
...tree
right: tree.right.delete(x)
}
}
}
}
}
}
fn main() {
mut tree := Tree[f64](Empty{})
vals := [0.2, 0.0, 0.5, 0.3, 0.6, 0.8, 0.9, 1.0, 0.1, 0.4, 0.7]
for i in vals {
tree = tree.insert(i)
}
println('[1] after insertion tree size is ${tree.size()}') // 11
del_vals := [-0.3, 0.0, 0.3, 0.6, 1.0, 1.5]
for i in del_vals {
tree = tree.delete(i)
}
print('[2] after deletion tree size is ${tree.size()}, ') // 7
print('and these elements were deleted: ') // 0.0 0.3 0.6 1.0
for i in vals {
if !tree.search(i) {
print('${i} ')
}
}
println('')
}