focus/list/arraylist/arraylist.go

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package arraylist
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import (
"fmt"
"strings"
"github.com/emirpasic/gods/lists"
"github.com/emirpasic/gods/utils"
)
func assertListImplementation() {
var _ lists.List = (*ArrayList)(nil)
}
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type ArrayList struct {
data []interface{}
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size int
}
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const (
growthFactor = float32(2.0) // growth by 100%
shrinkFactor = float32(0.25) // shrink when size is 25% of capacity (0 means never shrink)
)
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// New instantiates a new list and adds the passed values, if any, to the list
func New(values ...interface{}) *ArrayList {
list := &ArrayList{}
if len(values) > 0 {
list.Add(values...)
}
return list
}
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// Add appends a value at the end of the list
func (list *ArrayList) Add(values ...interface{}) {
list.growBy(len(values))
for _, value := range values {
list.data[list.size] = value
list.size++
}
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}
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// Get returns the element at index.
// Second return parameter is true if index is within bounds of the array and array is not empty, otherwise false.
func (list *ArrayList) Get(index int) (interface{}, bool) {
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if !list.withinRange(index) {
return nil, false
}
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return list.data[index], true
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}
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// Remove removes the element at the given index from the list.
func (list *ArrayList) Remove(index int) {
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if !list.withinRange(index) {
return
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}
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list.data[index] = nil // cleanup reference
copy(list.data[index:], list.data[index+1:list.size]) // shift to the left by one (slow operation, need ways to optimize this)
list.size--
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list.shrink()
}
// Contains checks if elements (one or more) are present in the set.
// All elements have to be present in the set for the method to return true.
// Performance time complexity of n^2.
// Returns true if no arguments are passed at all, i.e. set is always super-set of empty set.
func (list *ArrayList) Contains(values ...interface{}) bool {
for _, searchValue := range values {
found := false
for _, element := range list.data {
if element == searchValue {
found = true
break
}
}
if !found {
return false
}
}
return true
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}
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// Values returns all elements in the list.
func (list *ArrayList) Values() []interface{} {
newElements := make([]interface{}, list.size, list.size)
copy(newElements, list.data[:list.size])
return newElements
}
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//IndexOf returns index of provided element
func (list *ArrayList) IndexOf(value interface{}) int {
if list.size == 0 {
return -1
}
for index, element := range list.data {
if element == value {
return index
}
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}
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return -1
}
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// Empty returns true if list does not contain any elements.
func (list *ArrayList) Empty() bool {
return list.size == 0
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}
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// Size returns number of elements within the list.
func (list *ArrayList) Size() int {
return list.size
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}
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// Clear removes all elements from the list.
func (list *ArrayList) Clear() {
list.size = 0
list.data = []interface{}{}
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}
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// Sort sorts values (in-place) using.
func (list *ArrayList) Sort(comparator utils.Comparator) {
if len(list.data) < 2 {
return
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}
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utils.Sort(list.data[:list.size], comparator)
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}
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// Swap swaps the two values at the specified positions.
func (list *ArrayList) Swap(i, j int) {
if list.withinRange(i) && list.withinRange(j) {
list.data[i], list.data[j] = list.data[j], list.data[i]
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}
}
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// Insert inserts values at specified index position shifting the value at that position (if any) and any subsequent elements to the right.
// Does not do anything if position is negative or bigger than list's size
// Note: position equal to list's size is valid, i.e. append.
func (list *ArrayList) Insert(index int, values ...interface{}) {
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if !list.withinRange(index) {
// Append
if index == list.size {
list.Add(values...)
}
return
}
l := len(values)
list.growBy(l)
list.size += l
copy(list.data[index+l:], list.data[index:list.size-l])
copy(list.data[index:], values)
}
// Set the value at specified index
// Does not do anything if position is negative or bigger than list's size
// Note: position equal to list's size is valid, i.e. append.
func (list *ArrayList) Set(index int, value interface{}) {
if !list.withinRange(index) {
// Append
if index == list.size {
list.Add(value)
}
return
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}
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list.data[index] = value
}
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// String returns a string representation of container
func (list *ArrayList) String() string {
str := "ArrayList\n"
values := []string{}
for _, value := range list.data[:list.size] {
values = append(values, fmt.Sprintf("%v", value))
}
str += strings.Join(values, ", ")
return str
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}
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// Check that the index is within bounds of the list
func (list *ArrayList) withinRange(index int) bool {
return index >= 0 && index < list.size
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}
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func (list *ArrayList) resize(cap int) {
newElements := make([]interface{}, cap, cap)
copy(newElements, list.data)
list.data = newElements
}
// Expand the array if necessary, i.e. capacity will be reached if we add n elements
func (list *ArrayList) growBy(n int) {
// When capacity is reached, grow by a factor of growthFactor and add number of elements
currentCapacity := cap(list.data)
if list.size+n >= currentCapacity {
newCapacity := int(growthFactor * float32(currentCapacity+n))
list.resize(newCapacity)
}
}
// Shrink the array if necessary, i.e. when size is shrinkFactor percent of current capacity
func (list *ArrayList) shrink() {
if shrinkFactor == 0.0 {
return
}
// Shrink when size is at shrinkFactor * capacity
currentCapacity := cap(list.data)
if list.size <= int(float32(currentCapacity)*shrinkFactor) {
list.resize(list.size)
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}
}