417 lines
9.7 KiB
V
417 lines
9.7 KiB
V
// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module builtin
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// import strings
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// B-trees are balanced search trees with all leaves at
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// the same level. B-trees are generally faster than
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// binary search trees due to the better locality of
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// reference, since multiple keys are stored in one node.
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// The number for `degree` has been picked through vigor-
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// ous benchmarking but can be changed to any number > 1.
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// `degree` determines the size of each node.
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const (
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degree = 6
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mid_index = degree - 1
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max_size = 2 * degree - 1
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children_bytes = sizeof(voidptr) * (max_size + 1)
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)
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pub struct SortedMap {
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value_bytes int
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mut:
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root &mapnode
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pub mut:
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size int
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}
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struct mapnode {
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mut:
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keys [11]string // TODO: Should use `max_size`
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values [11]voidptr // TODO: Should use `max_size`
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children &voidptr
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size int
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}
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fn new_sorted_map(n, value_bytes int) SortedMap { // TODO: Remove `n`
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return SortedMap {
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value_bytes: value_bytes
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root: new_node()
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size: 0
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}
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}
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fn new_sorted_map_init(n, value_bytes int, keys &string, values voidptr) SortedMap {
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mut out := new_sorted_map(n, value_bytes)
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for i in 0 .. n {
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out.set(keys[i], byteptr(values) + i * value_bytes)
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}
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return out
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}
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// The tree is initialized with an empty node as root to
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// avoid having to check whether the root is null for
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// each insertion.
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fn new_node() &mapnode {
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return &mapnode {
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children: 0
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size: 0
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}
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}
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// This implementation does proactive insertion, meaning
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// that splits are done top-down and not bottom-up.
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fn (m mut SortedMap) set(key string, value voidptr) {
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mut node := m.root
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mut child_index := 0
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mut parent := &mapnode(0)
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for {
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if node.size == max_size {
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if isnil(parent) {
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parent = new_node()
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m.root = parent
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}
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parent.split_child(child_index, mut node)
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if key == parent.keys[child_index] {
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C.memcpy(parent.values[child_index], value, m.value_bytes)
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return
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}
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node = if key < parent.keys[child_index] {
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&mapnode(parent.children[child_index])
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} else {
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&mapnode(parent.children[child_index + 1])
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}
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}
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mut i := 0
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for i < node.size && key > node.keys[i] { i++ }
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if i != node.size && key == node.keys[i] {
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C.memcpy(node.values[i], value, m.value_bytes)
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return
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}
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if isnil(node.children) {
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mut j := node.size - 1
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for j >= 0 && key < node.keys[j] {
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node.keys[j + 1] = node.keys[j]
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node.values[j + 1] = node.values[j]
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j--
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}
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node.keys[j + 1] = key
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node.values[j + 1] = malloc(m.value_bytes)
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C.memcpy(node.values[j + 1], value, m.value_bytes)
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node.size++
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m.size++
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return
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}
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parent = node
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child_index = i
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node = &mapnode(node.children[child_index])
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}
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}
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fn (n mut mapnode) split_child(child_index int, y mut mapnode) {
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mut z := new_node()
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z.size = mid_index
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y.size = mid_index
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for j := mid_index - 1; j >= 0; j-- {
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z.keys[j] = y.keys[j + degree]
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z.values[j] = y.values[j + degree]
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}
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if !isnil(y.children) {
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z.children = &voidptr(malloc(children_bytes))
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for jj := degree - 1; jj >= 0; jj-- {
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z.children[jj] = y.children[jj + degree]
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}
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}
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if isnil(n.children) {
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n.children = &voidptr(malloc(children_bytes))
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}
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n.children[n.size + 1] = n.children[n.size]
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for j := n.size; j > child_index; j-- {
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n.keys[j] = n.keys[j - 1]
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n.values[j] = n.values[j - 1]
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n.children[j] = n.children[j - 1]
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}
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n.keys[child_index] = y.keys[mid_index]
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n.values[child_index] = y.values[mid_index]
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n.children[child_index] = voidptr(y)
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n.children[child_index + 1] = voidptr(z)
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n.size++
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}
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fn (m SortedMap) get(key string, out voidptr) bool {
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mut node := m.root
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for {
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mut i := node.size - 1
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for i >= 0 && key < node.keys[i] { i-- }
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if i != -1 && key == node.keys[i] {
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C.memcpy(out, node.values[i], m.value_bytes)
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return true
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}
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if isnil(node.children) {
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break
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}
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node = &mapnode(node.children[i + 1])
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}
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return false
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}
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fn (m SortedMap) exists(key string) bool {
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if isnil(m.root) { // TODO: find out why root can be nil
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return false
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}
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mut node := m.root
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for {
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mut i := node.size - 1
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for i >= 0 && key < node.keys[i] { i-- }
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if i != -1 && key == node.keys[i] {
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return true
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}
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if isnil(node.children) {
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break
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}
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node = &mapnode(node.children[i + 1])
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}
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return false
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}
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fn (n &mapnode) find_key(k string) int {
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mut idx := 0
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for idx < n.size && n.keys[idx] < k {
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idx++
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}
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return idx
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}
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fn (n mut mapnode) remove_key(k string) bool {
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idx := n.find_key(k)
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if idx < n.size && n.keys[idx] == k {
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if isnil(n.children) {
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n.remove_from_leaf(idx)
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} else {
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n.remove_from_non_leaf(idx)
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}
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return true
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} else {
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if isnil(n.children) {
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return false
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}
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flag := if idx == n.size {true} else {false}
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if (&mapnode(n.children[idx])).size < degree {
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n.fill(idx)
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}
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if flag && idx > n.size {
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return (&mapnode(n.children[idx - 1])).remove_key(k)
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} else {
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return (&mapnode(n.children[idx])).remove_key(k)
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}
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}
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}
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fn (n mut mapnode) remove_from_leaf(idx int) {
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for i := idx + 1; i < n.size; i++ {
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n.keys[i - 1] = n.keys[i]
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n.values[i - 1] = n.values[i]
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}
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n.size--
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}
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fn (n mut mapnode) remove_from_non_leaf(idx int) {
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k := n.keys[idx]
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if &mapnode(n.children[idx]).size >= degree {
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mut current := &mapnode(n.children[idx])
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for !isnil(current.children) {
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current = &mapnode(current.children[current.size])
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}
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predecessor := current.keys[current.size - 1]
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n.keys[idx] = predecessor
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n.values[idx] = current.values[current.size - 1]
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(&mapnode(n.children[idx])).remove_key(predecessor)
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} else if &mapnode(n.children[idx + 1]).size >= degree {
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mut current := &mapnode(n.children[idx + 1])
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for !isnil(current.children) {
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current = &mapnode(current.children[0])
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}
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successor := current.keys[0]
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n.keys[idx] = successor
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n.values[idx] = current.values[0]
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(&mapnode(n.children[idx + 1])).remove_key(successor)
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} else {
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n.merge(idx)
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(&mapnode(n.children[idx])).remove_key(k)
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}
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}
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fn (n mut mapnode) fill(idx int) {
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if idx != 0 && &mapnode(n.children[idx - 1]).size >= degree {
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n.borrow_from_prev(idx)
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} else if idx != n.size && &mapnode(n.children[idx + 1]).size >= degree {
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n.borrow_from_next(idx)
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} else if idx != n.size {
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n.merge(idx)
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} else {
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n.merge(idx - 1)
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}
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}
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fn (n mut mapnode) borrow_from_prev(idx int) {
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mut child := &mapnode(n.children[idx])
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mut sibling := &mapnode(n.children[idx - 1])
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for i := child.size - 1; i >= 0; i-- {
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child.keys[i + 1] = child.keys[i]
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child.values[i + 1] = child.values[i]
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}
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if !isnil(child.children) {
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for i := child.size; i >= 0; i-- {
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child.children[i + 1] = child.children[i]
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}
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}
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child.keys[0] = n.keys[idx - 1]
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child.values[0] = n.values[idx - 1]
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if !isnil(child.children) {
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child.children[0] = sibling.children[sibling.size]
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}
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n.keys[idx - 1] = sibling.keys[sibling.size - 1]
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n.values[idx - 1] = sibling.values[sibling.size - 1]
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child.size++
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sibling.size--
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}
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fn (n mut mapnode) borrow_from_next(idx int) {
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mut child := &mapnode(n.children[idx])
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mut sibling := &mapnode(n.children[idx + 1])
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child.keys[child.size] = n.keys[idx]
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child.values[child.size] = n.values[idx]
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if !isnil(child.children) {
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child.children[child.size + 1] = sibling.children[0]
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}
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n.keys[idx] = sibling.keys[0]
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n.values[idx] = sibling.values[0]
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for i := 1; i < sibling.size; i++ {
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sibling.keys[i - 1] = sibling.keys[i]
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sibling.values[i - 1] = sibling.values[i]
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}
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if !isnil(sibling.children) {
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for i := 1; i <= sibling.size; i++ {
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sibling.children[i - 1] = sibling.children[i]
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}
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}
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child.size++
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sibling.size--
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}
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fn (n mut mapnode) merge(idx int) {
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mut child := &mapnode(n.children[idx])
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sibling := &mapnode(n.children[idx + 1])
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child.keys[mid_index] = n.keys[idx]
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child.values[mid_index] = n.values[idx]
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for i in 0..sibling.size {
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child.keys[i + degree] = sibling.keys[i]
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child.values[i + degree] = sibling.values[i]
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}
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if !isnil(child.children) {
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for i := 0; i <= sibling.size; i++ {
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child.children[i + degree] = sibling.children[i]
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}
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}
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for i := idx + 1; i < n.size; i++ {
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n.keys[i - 1] = n.keys[i]
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n.values[i - 1] = n.values[i]
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}
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for i := idx + 2; i <= n.size; i++ {
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n.children[i - 1] = n.children[i]
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}
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child.size += sibling.size + 1
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n.size--
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// free(sibling)
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}
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pub fn (m mut SortedMap) delete(key string) {
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if m.root.size == 0 {
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return
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}
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removed := m.root.remove_key(key)
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if removed {
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m.size--
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}
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if m.root.size == 0 {
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// tmp := t.root
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if isnil(m.root.children) {
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return
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} else {
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m.root = &mapnode(m.root.children[0])
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}
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// free(tmp)
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}
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}
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// Insert all keys of the subtree into array `keys`
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// starting at `at`. Keys are inserted in order.
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fn (n &mapnode) subkeys(keys mut []string, at int) int {
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mut position := at
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if !isnil(n.children) {
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// Traverse children and insert
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// keys inbetween children
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for i in 0..n.size {
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child := &mapnode(n.children[i])
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position += child.subkeys(mut keys, position)
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keys[position] = n.keys[i]
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position++
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}
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// Insert the keys of the last child
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child := &mapnode(n.children[n.size])
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position += child.subkeys(mut keys, position)
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} else {
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// If leaf, insert keys
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for i in 0..n.size {
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keys[position + i] = n.keys[i]
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}
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position += n.size
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}
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// Return # of added keys
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return position - at
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}
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pub fn (m &SortedMap) keys() []string {
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mut keys := [''].repeat(m.size)
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if isnil(m.root) || m.root.size == 0 {
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return keys
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}
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m.root.subkeys(mut keys, 0)
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return keys
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}
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fn (n mut mapnode) free() {
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println('TODO')
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}
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pub fn (m mut SortedMap) free() {
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if isnil(m.root) {
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return
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}
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m.root.free()
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}
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pub fn (m SortedMap) print() {
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println('TODO')
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}
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// pub fn (m map_string) str() string {
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// if m.size == 0 {
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// return '{}'
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// }
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// mut sb := strings.new_builder(50)
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// sb.writeln('{')
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// for key, val in m {
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// sb.writeln(' "$key" => "$val"')
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// }
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// sb.writeln('}')
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// return sb.str()
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// }
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