mirror of
https://github.com/emirpasic/gods
synced 2024-11-08 13:10:26 +00:00
100 lines
2.8 KiB
Go
100 lines
2.8 KiB
Go
/*
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Copyright (c) Emir Pasic, All rights reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 3.0 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library. See the file LICENSE included
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with this distribution for more information.
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*/
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// Implementation of stack using a slice.
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// Structure is not thread safe.
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// References: http://en.wikipedia.org/wiki/Stack_%28abstract_data_type%29
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package arraystack
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import (
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"fmt"
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"github.com/emirpasic/gods/stacks"
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"strings"
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)
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func assertInterfaceImplementation() {
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var _ stacks.Interface = (*Stack)(nil)
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}
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type Stack struct {
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items []interface{}
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top int
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}
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// Instantiates a new empty stack
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func New() *Stack {
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return &Stack{top: -1}
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}
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// Pushes a value onto the top of the stack
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func (stack *Stack) Push(value interface{}) {
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// Increase when capacity is reached by a factor of 1.5 and add one so it grows when size is zero
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if stack.top+1 >= cap(stack.items) {
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currentSize := len(stack.items)
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sizeIncrease := int(1.5*float32(currentSize) + 1.0)
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newSize := currentSize + sizeIncrease
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newItems := make([]interface{}, newSize, newSize)
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copy(newItems, stack.items)
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stack.items = newItems
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}
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stack.top += 1
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stack.items[stack.top] = value
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}
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// Pops (removes) top element on stack and returns it, or nil if stack is empty.
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// Second return parameter is true, unless the stack was empty and there was nothing to pop.
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func (stack *Stack) Pop() (value interface{}, ok bool) {
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if stack.top >= 0 {
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value, ok = stack.items[stack.top], true
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// TODO shrink slice at some point
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stack.top -= 1
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return
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}
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return nil, false
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}
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// Returns top element on the stack without removing it, or nil if stack is empty.
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// Second return parameter is true, unless the stack was empty and there was nothing to peek.
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func (stack *Stack) Peek() (value interface{}, ok bool) {
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if stack.top >= 0 {
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return stack.items[stack.top], true
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}
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return nil, false
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}
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// Returns true if stack does not contain any elements.
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func (stack *Stack) Empty() bool {
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return stack.Size() == 0
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}
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// Returns number of elements within the stack.
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func (stack *Stack) Size() int {
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return stack.top + 1
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}
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func (stack *Stack) String() string {
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str := "ArrayStack\n"
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values := []string{}
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for _, value := range stack.items {
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values = append(values, fmt.Sprintf("%v", value))
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}
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str += strings.Join(values, ", ")
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return str
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}
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