cheat/vendor/github.com/emirpasic/gods/trees/binaryheap/iterator.go

144 lines
4.7 KiB
Go

// Copyright (c) 2015, Emir Pasic. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package binaryheap
import (
"github.com/emirpasic/gods/containers"
)
// Assert Iterator implementation
var _ containers.ReverseIteratorWithIndex = (*Iterator)(nil)
// Iterator returns a stateful iterator whose values can be fetched by an index.
type Iterator struct {
heap *Heap
index int
}
// Iterator returns a stateful iterator whose values can be fetched by an index.
func (heap *Heap) Iterator() Iterator {
return Iterator{heap: heap, index: -1}
}
// Next moves the iterator to the next element and returns true if there was a next element in the container.
// If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
// Modifies the state of the iterator.
func (iterator *Iterator) Next() bool {
if iterator.index < iterator.heap.Size() {
iterator.index++
}
return iterator.heap.withinRange(iterator.index)
}
// Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
// If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) Prev() bool {
if iterator.index >= 0 {
iterator.index--
}
return iterator.heap.withinRange(iterator.index)
}
// Value returns the current element's value.
// Does not modify the state of the iterator.
func (iterator *Iterator) Value() interface{} {
start, end := evaluateRange(iterator.index)
if end > iterator.heap.Size() {
end = iterator.heap.Size()
}
tmpHeap := NewWith(iterator.heap.Comparator)
for n := start; n < end; n++ {
value, _ := iterator.heap.list.Get(n)
tmpHeap.Push(value)
}
for n := 0; n < iterator.index-start; n++ {
tmpHeap.Pop()
}
value, _ := tmpHeap.Pop()
return value
}
// Index returns the current element's index.
// Does not modify the state of the iterator.
func (iterator *Iterator) Index() int {
return iterator.index
}
// Begin resets the iterator to its initial state (one-before-first)
// Call Next() to fetch the first element if any.
func (iterator *Iterator) Begin() {
iterator.index = -1
}
// End moves the iterator past the last element (one-past-the-end).
// Call Prev() to fetch the last element if any.
func (iterator *Iterator) End() {
iterator.index = iterator.heap.Size()
}
// First moves the iterator to the first element and returns true if there was a first element in the container.
// If First() returns true, then first element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) First() bool {
iterator.Begin()
return iterator.Next()
}
// Last moves the iterator to the last element and returns true if there was a last element in the container.
// If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) Last() bool {
iterator.End()
return iterator.Prev()
}
// NextTo moves the iterator to the next element from current position that satisfies the condition given by the
// passed function, and returns true if there was a next element in the container.
// If NextTo() returns true, then next element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) NextTo(f func(index int, value interface{}) bool) bool {
for iterator.Next() {
index, value := iterator.Index(), iterator.Value()
if f(index, value) {
return true
}
}
return false
}
// PrevTo moves the iterator to the previous element from current position that satisfies the condition given by the
// passed function, and returns true if there was a next element in the container.
// If PrevTo() returns true, then next element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) PrevTo(f func(index int, value interface{}) bool) bool {
for iterator.Prev() {
index, value := iterator.Index(), iterator.Value()
if f(index, value) {
return true
}
}
return false
}
// numOfBits counts the number of bits of an int
func numOfBits(n int) uint {
var count uint
for n != 0 {
count++
n >>= 1
}
return count
}
// evaluateRange evaluates the index range [start,end) of same level nodes in the heap as the index
func evaluateRange(index int) (start int, end int) {
bits := numOfBits(index+1) - 1
start = 1<<bits - 1
end = start + 1<<bits
return
}