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v/examples/binary_search_tree.v

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V

// Binary Search Tree example by @SleepyRoy
// TODO: make Node.value generic once it's robust enough
// TODO: `return match` instead of returns everywhere inside match
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 {
// TODO: remove int() once match gets smarter
Empty { int(0) }
Node { 1 + size(tree.left) + size(tree.right) }
}
}
// insert a value to BST
fn insert(tree Tree, x f64) Tree {
match tree {
Empty { return Node{x, tree, tree} }
Node {
return 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 {
match tree {
Empty { return false }
Node {
return 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 {
match tree {
Empty { return 1e100 }
Node { return 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 {
match tree {
Empty { return tree }
Node {
if tree.left is Node && tree.right is Node {
return 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 {
return if x == tree.value { tree.left } else { Node{...tree, left: delete(tree.left, x)} }
} else {
if x == tree.value { return tree.right } else { return Node{...tree, right: delete(tree.right, x)} }
}
}
}
}
fn main() {
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('')
}