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Copy pathsolution.go
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127 lines (115 loc) · 2.57 KB
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Copy pathsolution.go
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127 lines (115 loc) · 2.57 KB
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package main
import "fmt"
// TODO: implement a queue with a dynamicly sized ring-buffer storage.
type Queue struct {
buffer []int
begin, length int
}
func (queue *Queue) PushBack(data int) {
queue.ensureAvailable(1)
pos := queue.begin + queue.length
if pos >= len(queue.buffer) {
pos -= len(queue.buffer)
}
queue.buffer[pos] = data
queue.length++
}
func (queue *Queue) PopFront() (result int) {
if queue.Empty() {
return 0
}
result = queue.buffer[queue.begin]
queue.length--
queue.begin++
if queue.begin >= len(queue.buffer) {
queue.begin = 0
}
return
}
func (queue *Queue) Empty() bool {
return queue.Len() == 0
}
func (queue *Queue) Len() int {
return queue.length
}
func (queue *Queue) ensureAvailable(available int) {
//fmt.Println(len(queue.buffer), queue.length, available)
if queue.buffer == nil {
to_allocate := available
if to_allocate < 16 {
to_allocate = 16
}
queue.buffer = make([]int, to_allocate)
queue.begin = 0
queue.length = 0
} else if len(queue.buffer) < queue.length + available {
//fmt.Println("Growing buffer")
new_buffer := make([]int, (queue.length + available) * 3/2)
if queue.begin + queue.length < len(queue.buffer) {
copy(new_buffer, queue.buffer[queue.begin:queue.begin + queue.length])
} else {
// 2 parts, wrapped
p1begin := queue.begin
p1len := len(queue.buffer) - p1begin
p2begin := 0
p2len := queue.length - p1len
// copy p1 to the start of new_buffer
copy(new_buffer, queue.buffer[p1begin:p1begin + p1len])
// append p2 to new_buffer
copy(new_buffer[p1len:len(new_buffer)], queue.buffer[p2begin:p2begin + p2len])
}
queue.buffer = new_buffer
queue.begin = 0
}
}
func main() {
queue := new(Queue)
if !queue.Empty() {
panic("!queue.Empty()")
}
queue.PushBack(1)
queue.PushBack(2)
queue.PushBack(3)
if queue.Empty() {
panic("queue.Empty()")
}
if queue.PopFront() != 1 {
panic("queue.PopFront() != 1")
}
if queue.PopFront() != 2 {
panic("queue.PopFront() != 2")
}
if queue.PopFront() != 3 {
panic("queue.PopFront() != 3")
}
if !queue.Empty() {
panic("!queue.Empty()")
}
queue.PushBack(4)
if queue.Empty() {
panic("queue.Empty()")
}
if queue.PopFront() != 4 {
panic("queue.PopFront() != 4")
}
in := 0
out := 0
for i := 1; i < 100; i++ {
for j := 0; j < i; j++ {
queue.PushBack(in)
in++
}
x := queue.PopFront()
if x != out {
panic(fmt.Sprintf("queue.PopFront() != %d, got %d", out, x))
}
out++
}
for !queue.Empty() {
x := queue.PopFront()
if x != out {
panic(fmt.Sprintf("queue.PopFront() != %d, got %d", out, x))
}
out++
}
}