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113 lines
3.3 KiB
113 lines
3.3 KiB
// CookieJar - A contestant's algorithm toolbox
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// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
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//
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// CookieJar is dual licensed: use of this source code is governed by a BSD
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// license that can be found in the LICENSE file. Alternatively, the CookieJar
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// toolbox may be used in accordance with the terms and conditions contained
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// in a signed written agreement between you and the author(s).
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// This is a duplicated and slightly modified version of "gopkg.in/karalabe/cookiejar.v2/collections/prque".
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package prque
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import "cmp"
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// The size of a block of data
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const blockSize = 4096
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// A prioritized item in the sorted stack.
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type item[P cmp.Ordered, V any] struct {
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value V
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priority P
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}
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// SetIndexCallback is called when the element is moved to a new index.
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// Providing SetIndexCallback is optional, it is needed only if the application needs
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// to delete elements other than the top one.
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type SetIndexCallback[V any] func(data V, index int)
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// Internal sortable stack data structure. Implements the Push and Pop ops for
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// the stack (heap) functionality and the Len, Less and Swap methods for the
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// sortability requirements of the heaps.
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type sstack[P cmp.Ordered, V any] struct {
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setIndex SetIndexCallback[V]
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size int
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capacity int
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offset int
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blocks [][]*item[P, V]
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active []*item[P, V]
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}
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// Creates a new, empty stack.
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func newSstack[P cmp.Ordered, V any](setIndex SetIndexCallback[V]) *sstack[P, V] {
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result := new(sstack[P, V])
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result.setIndex = setIndex
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result.active = make([]*item[P, V], blockSize)
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result.blocks = [][]*item[P, V]{result.active}
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result.capacity = blockSize
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return result
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}
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// Push a value onto the stack, expanding it if necessary. Required by
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// heap.Interface.
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func (s *sstack[P, V]) Push(data any) {
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if s.size == s.capacity {
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s.active = make([]*item[P, V], blockSize)
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s.blocks = append(s.blocks, s.active)
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s.capacity += blockSize
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s.offset = 0
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} else if s.offset == blockSize {
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s.active = s.blocks[s.size/blockSize]
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s.offset = 0
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}
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if s.setIndex != nil {
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s.setIndex(data.(*item[P, V]).value, s.size)
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}
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s.active[s.offset] = data.(*item[P, V])
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s.offset++
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s.size++
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}
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// Pop a value off the stack and returns it. Currently no shrinking is done.
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// Required by heap.Interface.
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func (s *sstack[P, V]) Pop() (res any) {
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s.size--
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s.offset--
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if s.offset < 0 {
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s.offset = blockSize - 1
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s.active = s.blocks[s.size/blockSize]
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}
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res, s.active[s.offset] = s.active[s.offset], nil
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if s.setIndex != nil {
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s.setIndex(res.(*item[P, V]).value, -1)
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}
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return
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}
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// Len returns the length of the stack. Required by sort.Interface.
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func (s *sstack[P, V]) Len() int {
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return s.size
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}
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// Less compares the priority of two elements of the stack (higher is first).
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// Required by sort.Interface.
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func (s *sstack[P, V]) Less(i, j int) bool {
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return s.blocks[i/blockSize][i%blockSize].priority > s.blocks[j/blockSize][j%blockSize].priority
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}
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// Swap two elements in the stack. Required by sort.Interface.
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func (s *sstack[P, V]) Swap(i, j int) {
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ib, io, jb, jo := i/blockSize, i%blockSize, j/blockSize, j%blockSize
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a, b := s.blocks[jb][jo], s.blocks[ib][io]
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if s.setIndex != nil {
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s.setIndex(a.value, i)
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s.setIndex(b.value, j)
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}
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s.blocks[ib][io], s.blocks[jb][jo] = a, b
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}
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// Reset the stack, effectively clearing its contents.
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func (s *sstack[P, V]) Reset() {
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*s = *newSstack[P, V](s.setIndex)
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}
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