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// Binary Search Tree example by @SleepyRoy
// TODO: make Node.value generic once it's robust enough
struct Empty {}
struct Node {
value f64
left Tree
right Tree
}
type Tree = Empty | Node
// return size(number of nodes) of BST
fn size(tree Tree) int {
return match tree {
Empty { 0 }
Node { 1 + size(tree.left) + size(tree.right) }
}
}
// insert a value to BST
fn insert(tree Tree, x f64) Tree {
return match tree {
Empty {
Node{x, tree, tree}
}
Node {
if x == tree.value {
tree
} else if x < tree.value {
Node{
...tree
left: insert(tree.left, x)
}
} else {
Node{
...tree
right: insert(tree.right, x)
}
}
}
}
}
// whether able to find a value in BST
fn search(tree Tree, x f64) bool {
return match tree {
Empty {
false
}
Node {
if x == tree.value {
true
} else if x < tree.value {
search(tree.left, x)
} else {
search(tree.right, x)
}
}
}
}
// find the minimal value of a BST
fn min(tree Tree) f64 {
return match tree {
Empty {
1e100
}
Node {
if tree.value < min(tree.left) {
tree.value
} else {
min(tree.left)
}
}
}
}
// delete a value in BST (if nonexistant do nothing)
fn delete(tree Tree, x f64) Tree {
return match tree {
Empty {
tree
}
Node {
if tree.left is Node && tree.right is Node {
if x < tree.value {
Node{
...tree
left: delete(tree.left, x)
}
} else if x > tree.value {
Node{
...tree
right: delete(tree.right, x)
}
} else {
Node{
...tree
value: min(tree.right)
right: delete(tree.right, min(tree.right))
}
}
} else if tree.left is Node {
if x == tree.value {
tree.left
} else {
Node{
...tree
left: delete(tree.left, x)
}
}
} else {
if x == tree.value {
tree.right
} else {
Node{
...tree
right: delete(tree.right, x)
}
}
}
}
}
}
fn main() {
$if !freestanding {
mut tree := Tree(Empty{})
input := [0.3, 0.2, 0.5, 0.0, 0.6, 0.8, 0.9, 1.0, 0.1, 0.4, 0.7]
for i in input {
tree = insert(tree, i)
}
println('[1] after insertion tree size is ${size(tree)}') // 11
del := [-0.3, 0.0, 0.3, 0.6, 1.0, 1.5]
for i in del {
tree = delete(tree, i)
}
print('[2] after deletion tree size is ${size(tree)}, ') // 7
print('and these elements were deleted: ') // 0.0 0.3 0.6 1.0
for i in input {
if !search(tree, i) {
print('$i ')
}
}
println('')
} $else {
mut tree := Tree(Empty{})
input := [0.3, 0.2, 0.5, 0.0, 0.6, 0.8, 0.9, 1.0, 0.1, 0.4, 0.7]
for i in input {
tree = insert(tree, i)
}
print('[1] after insertion tree size is ') // 11
println(size(tree))
del := [-0.3, 0.0, 0.3, 0.6, 1.0, 1.5]
for i in del {
tree = delete(tree, i)
}
print('[2] after deletion tree size is ') // 7
print(size(tree))
print(', and these elements were deleted: ') // 0.0 0.3 0.6 1.0
for i in input {
if !search(tree, i) {
print(i)
print(' ')
}
}
println('')
}
}
|
