手撸golang 基本数据结构与算法 数组

Posted 2021-10-05 ioly

手撸golang 基本数据结构与算法 数组

缘起

最近阅读<<我的第一本算法书>>(【日】石田保辉；宫崎修一)
本系列笔记拟采用golang练习之

数组

数组是一种线性数据结构,
数据按顺序存储在内存的连续空间内。
每个数据的内存地址（在内存上的位置）都可以通过数组下标算出，
我们也就可以借此直接访问目标数据（这叫作“随机访问”）。

访问数据时使用的是随机访问（通过下标可计算出内存地址），
所以需要的运行时间仅为恒定的O(1)。
但另一方面，想要向数组中添加新数据时，必须把目标位置后面的数据一个个移开。
所以，如果在数组头部添加数据，就需要O(n)的时间。
删除操作同理。

摘自 <<我的第一本算法书>>(【日】石田保辉；宫崎修一)

目标

• golang自带数组和slice, 但操作方法不够OO, 本练习拟创建更OO的数组接口和方法

设计

• IArray: 定义数组的接口
• IArrayIterator: 定义数组的迭代器
• tCustomArray: 数组的OO封装, 实现IArray接口
• tArrayIterator: 数组迭代器, 实现IArrayIterator接口

单元测试

array_test.go

package data_structure

import (
    "learning/gooop/data_structure/array"
    "testing"
)

func Test_Array(t *testing.T) {
    fnAssertTrue := func(b bool, msg string) {
        if !b {
            t.Fatal(msg)
        }
    }

    it := array.NewArray()
    t.Log(it.String())
    fnAssertTrue(it.String() == "[]", "expecting []")

    it.Append(1)
    t.Log(it.String())
    fnAssertTrue(it.String() == "[1]", "expecting [1]")

    e := it.Remove(0)
    t.Log(it.String())
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(it.String() == "[]", "expecting []")

    e = it.Insert(0, 1)
    t.Log(it.String())
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(it.String() == "[1]", "expecting [1]")

    e = it.Insert(0, 0)
    t.Log(it.String())
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(it.String() == "[0,1]", "expecting [0,1]")

    e = it.Insert(2, 2)
    t.Log(it.String())
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(it.String() == "[0,1,2]", "expecting [0,1,2]")

    e = it.Set(0, 10)
    t.Log(it.String())
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(it.String() == "[10,1,2]", "expecting [10,1,2]")

    e = it.Set(2, 20)
    t.Log(it.String())
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(it.String() == "[10,1,20]", "expecting [10,1,20]")

    e,x := it.Get(0)
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(x == 10, "expecting 10")

    e,x = it.Get(2)
    fnAssertTrue(e == nil, "expecting e == nil")
    fnAssertTrue(x == 20, "expecting 20")

    e,_ = it.Get(3)
    fnAssertTrue(e != nil, "expecting e != nil")

    e,_ = it.Get(-1)
    fnAssertTrue(e != nil, "expecting e != nil")
}

测试输出

$ go test -v array_test.go 
=== RUN   Test_Array
    array_test.go:16: []
    array_test.go:20: [1]
    array_test.go:24: []
    array_test.go:29: [1]
    array_test.go:34: [0,1]
    array_test.go:39: [0,1,2]
    array_test.go:44: [10,1,2]
    array_test.go:49: [10,1,20]
--- PASS: Test_Array (0.00s)
PASS
ok      command-line-arguments  0.002s

IArray.go

定义数组的接口

package array

type IArray interface {
    Size() int
    IsEmpty() bool
    IsNotEmpty() bool

    Get(i int) (error,interface{})
    Set(i int, it interface{}) error

    Append(it interface{})
    Remove(i int) error
    Insert(i int, it interface{}) error
    Iterator() IArrayIterator

    String() string
}

IArrayIterator.go

定义数组的迭代器

package array

type IArrayIterator interface {
    More() bool
    Next() (error,interface{})
}

tCustomArray.go

数组的OO封装, 实现IArray接口

package array

import (
    "errors"
    "fmt"
    "strings"
)

type tCustomArray struct {
    items []interface{}
    size int
}

var gIndexOutofBoundsError = errors.New("index out of bounds")

func NewArray() IArray {
    return &tCustomArray{
        items: make([]interface{}, 0),
        size: 0,
    }
}

func (me *tCustomArray) Size() int {
    return me.size
}

func (me *tCustomArray) IsEmpty() bool {
    return me.size <= 0
}

func (me *tCustomArray) IsNotEmpty() bool {
    return !me.IsEmpty()
}

func (me *tCustomArray) Get(i int) (error,interface{}) {
    if i >= me.size || i < 0 {
        return gIndexOutofBoundsError, nil
    }
    return nil, me.items[i]
}

func (me *tCustomArray) Set(i int, it interface{}) error {
    if i >= me.size || i < 0 {
        return gIndexOutofBoundsError
    }
    me.items[i] = it
    return nil
}

func (me *tCustomArray) Append(it interface{}) {
    me.items = append(me.items, it)
    me.size++
}

func (me *tCustomArray) Remove(i int) error {
    if i >= me.size || i < 0 {
        return gIndexOutofBoundsError
    }

    me.items = append(me.items[:i], me.items[i+1:]...)
    me.size--

    return nil
}


func (me *tCustomArray) Insert(i int, it interface{}) error {
    if i > me.size || i < 0 {
        return gIndexOutofBoundsError
    }

    newItems := make([]interface{}, 0)
    newItems = append(newItems, me.items[:i]...)
    newItems = append(newItems, it)
    newItems = append(newItems, me.items[i:]...)

    me.items = newItems
    me.size++
    return nil
}


func (me *tCustomArray) Iterator() IArrayIterator {
    return newArrayIterator(me.items)
}

func (me *tCustomArray) String() string {
    ss := make([]string, me.size)
    for i,it := range me.items {
        ss[i] = fmt.Sprintf("%v", it)
    }
    return fmt.Sprintf("[%s]", strings.Join(ss, ","))
}

tArrayIterator.go

数组迭代器, 实现IArrayIterator接口

package array

type tArrayIterator struct {
    items []interface{}
    count int
    pos int
}

func newArrayIterator(items []interface{}) IArrayIterator {
    size := len(items)
    copy := make([]interface{}, size)
    for i,it := range items {
        copy[i] = it
    }

    return &tArrayIterator{
        items: copy,
        count: size,
        pos: 0,
    }
}


func (me *tArrayIterator) More() bool {
    return me.pos < me.count
}

func (me *tArrayIterator) Next() (error,interface{}) {
    if me.pos >= me.count {
        return gIndexOutofBoundsError, nil
    }

    n := me.pos
    me.pos++
    return nil, me.items[n]
}

(end)