mirror of
https://github.com/emirpasic/gods
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112 lines
3.2 KiB
Go
112 lines
3.2 KiB
Go
// Copyright (c) 2017, Benjamin Scher Purcell. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package avltree
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import "github.com/emirpasic/gods/containers"
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func assertIteratorImplementation() {
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var _ containers.ReverseIteratorWithKey = (*Iterator)(nil)
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}
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// Iterator holding the iterator's state
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type Iterator struct {
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tree *Tree
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node *Node
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position position
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}
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type position byte
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const (
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begin, between, end position = 0, 1, 2
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)
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// Iterator returns a stateful iterator whose elements are key/value pairs.
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func (tree *Tree) Iterator() containers.ReverseIteratorWithKey {
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return &Iterator{tree: tree, node: nil, position: begin}
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}
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// Next moves the iterator to the next element and returns true if there was a next element in the container.
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// If Next() returns true, then next element's key and value can be retrieved by Key() and Value().
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// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
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// Modifies the state of the iterator.
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func (iter *Iterator) Next() bool {
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switch iter.position {
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case begin:
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iter.position = between
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iter.node = iter.tree.Left()
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case between:
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iter.node = iter.node.Next()
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}
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if iter.node == nil {
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iter.position = end
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return false
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}
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return true
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}
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// Prev moves the iterator to the next element and returns true if there was a previous element in the container.
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// If Prev() returns true, then next element's key and value can be retrieved by Key() and Value().
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// If Prev() was called for the first time, then it will point the iterator to the first element if it exists.
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// Modifies the state of the iterator.
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func (iter *Iterator) Prev() bool {
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switch iter.position {
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case end:
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iter.position = between
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iter.node = iter.tree.Right()
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case between:
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iter.node = iter.node.Prev()
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}
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if iter.node == nil {
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iter.position = begin
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return false
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}
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return true
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}
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// Value returns the current element's value.
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// Does not modify the state of the iterator.
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func (iter *Iterator) Value() interface{} {
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return iter.node.Value
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}
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// Key returns the current element's key.
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// Does not modify the state of the iterator.
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func (iter *Iterator) Key() interface{} {
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return iter.node.Key
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}
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// Begin resets the iterator to its initial state (one-before-first)
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// Call Next() to fetch the first element if any.
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func (iter *Iterator) Begin() {
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iter.node = nil
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iter.position = begin
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}
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// End moves the iterator past the last element (one-past-the-end).
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// Call Prev() to fetch the last element if any.
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func (iter *Iterator) End() {
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iter.node = nil
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iter.position = end
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}
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// First moves the iterator to the first element and returns true if there was a first element in the container.
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// If First() returns true, then first element's key and value can be retrieved by Key() and Value().
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// Modifies the state of the iterator
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func (iter *Iterator) First() bool {
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iter.Begin()
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return iter.Next()
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}
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// Last moves the iterator to the last element and returns true if there was a last element in the container.
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// If Last() returns true, then last element's key and value can be retrieved by Key() and Value().
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// Modifies the state of the iterator.
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func (iter *Iterator) Last() bool {
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iter.End()
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return iter.Prev()
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}
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