89 lines
2.3 KiB
Go
89 lines
2.3 KiB
Go
|
// CookieJar - A contestant's algorithm toolbox
|
||
|
|
// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
|
||
|
|
//
|
||
|
|
// CookieJar is dual licensed: use of this source code is governed by a BSD
|
||
|
|
// license that can be found in the LICENSE file. Alternatively, the CookieJar
|
||
|
|
// toolbox may be used in accordance with the terms and conditions contained
|
||
|
|
// in a signed written agreement between you and the author(s).
|
||
|
|
|
||
|
|
// Package stack implements a LIFO (last in first out) data structure supporting
|
||
|
|
// arbitrary types (even a mixture).
|
||
|
|
//
|
||
|
|
// Internally it uses a dynamically growing slice of blocks, resulting in faster
|
||
|
|
// resizes than a simple dynamic array/slice would allow.
|
||
|
|
package stack
|
||
|
|
|
||
|
|
// The size of a block of data
|
||
|
|
const blockSize = 4096
|
||
|
|
|
||
|
|
// Last in, first out data structure.
|
||
|
|
type Stack struct {
|
||
|
|
size int
|
||
|
|
capacity int
|
||
|
|
offset int
|
||
|
|
|
||
|
|
blocks [][]interface{}
|
||
|
|
active []interface{}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Creates a new, empty stack.
|
||
|
|
func New() *Stack {
|
||
|
|
result := new(Stack)
|
||
|
|
result.active = make([]interface{}, blockSize)
|
||
|
|
result.blocks = [][]interface{}{result.active}
|
||
|
|
result.capacity = blockSize
|
||
|
|
return result
|
||
|
|
}
|
||
|
|
|
||
|
|
// Pushes a value onto the stack, expanding it if necessary.
|
||
|
|
func (s *Stack) Push(data interface{}) {
|
||
|
|
if s.size == s.capacity {
|
||
|
|
s.active = make([]interface{}, blockSize)
|
||
|
|
s.blocks = append(s.blocks, s.active)
|
||
|
|
s.capacity += blockSize
|
||
|
|
s.offset = 0
|
||
|
|
} else if s.offset == blockSize {
|
||
|
|
s.active = s.blocks[s.size/blockSize]
|
||
|
|
s.offset = 0
|
||
|
|
}
|
||
|
|
s.active[s.offset] = data
|
||
|
|
s.offset++
|
||
|
|
s.size++
|
||
|
|
}
|
||
|
|
|
||
|
|
// Pops a value off the stack and returns it. Currently no shrinking is done.
|
||
|
|
func (s *Stack) Pop() (res interface{}) {
|
||
|
|
s.size--
|
||
|
|
s.offset--
|
||
|
|
if s.offset < 0 {
|
||
|
|
s.offset = blockSize - 1
|
||
|
|
s.active = s.blocks[s.size/blockSize]
|
||
|
|
}
|
||
|
|
res, s.active[s.offset] = s.active[s.offset], nil
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
// Returns the value currently on the top of the stack. No bounds are checked.
|
||
|
|
func (s *Stack) Top() interface{} {
|
||
|
|
if s.offset > 0 {
|
||
|
|
return s.active[s.offset-1]
|
||
|
|
} else {
|
||
|
|
return s.blocks[(s.size-1)/blockSize][blockSize-1]
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Checks whether the stack is empty or not.
|
||
|
|
func (s *Stack) Empty() bool {
|
||
|
|
return s.size == 0
|
||
|
|
}
|
||
|
|
|
||
|
|
// Returns the number of elements in the stack.
|
||
|
|
func (s *Stack) Size() int {
|
||
|
|
return s.size
|
||
|
|
}
|
||
|
|
|
||
|
|
// Resets the stack, effectively clearing its contents.
|
||
|
|
func (s *Stack) Reset() {
|
||
|
|
*s = *New()
|
||
|
|
}
|