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