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2023-06-26 17:30:52 +00:00
< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "../index.html" > Go语言圣经< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../preface-zh.html" > 译者序< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../preface.html" > 前言< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1.html" > < strong aria-hidden = "true" > 1.< / strong > 入门< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-01.html" > < strong aria-hidden = "true" > 1.1.< / strong > Hello, World< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-02.html" > < strong aria-hidden = "true" > 1.2.< / strong > 命令行参数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-03.html" > < strong aria-hidden = "true" > 1.3.< / strong > 查找重复的行< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-04.html" > < strong aria-hidden = "true" > 1.4.< / strong > GIF动画< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-05.html" > < strong aria-hidden = "true" > 1.5.< / strong > 获取URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-06.html" > < strong aria-hidden = "true" > 1.6.< / strong > 并发获取多个URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-07.html" > < strong aria-hidden = "true" > 1.7.< / strong > Web服务< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-08.html" > < strong aria-hidden = "true" > 1.8.< / strong > 本章要点< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2.html" > < strong aria-hidden = "true" > 2.< / strong > 程序结构< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-01.html" > < strong aria-hidden = "true" > 2.1.< / strong > 命名< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-02.html" > < strong aria-hidden = "true" > 2.2.< / strong > 声明< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-03.html" > < strong aria-hidden = "true" > 2.3.< / strong > 变量< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-04.html" > < strong aria-hidden = "true" > 2.4.< / strong > 赋值< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-05.html" > < strong aria-hidden = "true" > 2.5.< / strong > 类型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-06.html" > < strong aria-hidden = "true" > 2.6.< / strong > 包和文件< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-07.html" > < strong aria-hidden = "true" > 2.7.< / strong > 作用域< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3.html" > < strong aria-hidden = "true" > 3.< / strong > 基础数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-01.html" > < strong aria-hidden = "true" > 3.1.< / strong > 整型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-02.html" > < strong aria-hidden = "true" > 3.2.< / strong > 浮点数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-03.html" > < strong aria-hidden = "true" > 3.3.< / strong > 复数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-04.html" > < strong aria-hidden = "true" > 3.4.< / strong > 布尔型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-05.html" > < strong aria-hidden = "true" > 3.5.< / strong > 字符串< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-06.html" > < strong aria-hidden = "true" > 3.6.< / strong > 常量< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4.html" > < strong aria-hidden = "true" > 4.< / strong > 复合数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-01.html" > < strong aria-hidden = "true" > 4.1.< / strong > 数组< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-02.html" > < strong aria-hidden = "true" > 4.2.< / strong > Slice< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-03.html" > < strong aria-hidden = "true" > 4.3.< / strong > Map< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-04.html" > < strong aria-hidden = "true" > 4.4.< / strong > 结构体< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-05.html" > < strong aria-hidden = "true" > 4.5.< / strong > JSON< /
2022-08-04 06:59:33 +00:00
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2024-06-12 07:20:07 +00:00
< li > < em > Go语言圣经读书笔记(挖坑中...): < a href = "https://github.com/chai2010/gopl-notes-zh" > https://github.com/chai2010/gopl-notes-zh< / a > < / em > < / li >
< li > < em > 凹语言(Go实现, 面向WASM设计): < a href = "https://github.com/wa-lang/wa" > https://github.com/wa-lang/wa< / a > < / em > < / li >
2023-06-26 17:46:27 +00:00
< / ul >
2022-08-04 06:59:33 +00:00
< hr >
< h2 id = "76-sortinterface接口" > < a class = "header" href = "#76-sortinterface接口" > 7.6. sort.Interface接口< / a > < / h2 >
< p > 排序操作和字符串格式化一样是很多程序经常使用的操作。尽管一个最短的快排程序只要15行就可以搞定， ， < / p >
< p > 幸运的是， ， ， ， ， ， < / p >
< p > 一个内置的排序算法需要知道三个东西： ， ， ； ： < / p >
< pre > < code class = "language-go" > package sort
type Interface interface {
Len() int
Less(i, j int) bool // i, j are indices of sequence elements
Swap(i, j int)
}
< / code > < / pre >
< p > 为了对序列进行排序， ， ， ， < / p >
< pre > < code class = "language-go" > type StringSlice []string
func (p StringSlice) Len() int { return len(p) }
func (p StringSlice) Less(i, j int) bool { return p[i] < p[j] }
func (p StringSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
< / code > < / pre >
< p > 现在我们可以通过像下面这样将一个切片转换为一个StringSlice类型来进行排序： < / p >
< pre > < code class = "language-go" > sort.Sort(StringSlice(names))
< / code > < / pre >
< p > 这个转换得到一个相同长度， ， ； < / p >
< p > 对字符串切片的排序是很常用的需要， ， < / p >
< p > 这里用到的技术很容易适用到其它排序序列中， （ ， ） ， ， < / p >
< p > 我们会运行上面的例子来对一个表格中的音乐播放列表进行排序。每个track都是单独的一行， ， ， ， ； < / p >
< p > 下面的变量tracks包含了一个播放列表。（ ’ ） ， ， ， < / p >
< p > < u > < i > gopl.io/ch7/sorting< / i > < / u > < / p >
< pre > < code class = "language-go" > type Track struct {
Title string
Artist string
Album string
Year int
Length time.Duration
}
var tracks = []*Track{
{" Go" , " Delilah" , " From the Roots Up" , 2012, length(" 3m38s" )},
{" Go" , " Moby" , " Moby" , 1992, length(" 3m37s" )},
{" Go Ahead" , " Alicia Keys" , " As I Am" , 2007, length(" 4m36s" )},
{" Ready 2 Go" , " Martin Solveig" , " Smash" , 2011, length(" 4m24s" )},
}
func length(s string) time.Duration {
d, err := time.ParseDuration(s)
if err != nil {
panic(s)
}
return d
}
< / code > < / pre >
< p > printTracks函数将播放列表打印成一个表格。一个图形化的展示可能会更好点， ， < code > *tabwriter.Writer< / code > 是满足io.Writer接口的。它会收集每一片写向它的数据； （ ） < / p >
< pre > < code class = "language-go" > func printTracks(tracks []*Track) {
const format = " %v\t%v\t%v\t%v\t%v\t\n"
tw := new(tabwriter.Writer).Init(os.Stdout, 0, 8, 2, ' ', 0)
fmt.Fprintf(tw, format, " Title" , " Artist" , " Album" , " Year" , " Length" )
fmt.Fprintf(tw, format, " -----" , " ------" , " -----" , " ----" , " ------" )
for _, t := range tracks {
fmt.Fprintf(tw, format, t.Title, t.Artist, t.Album, t.Year, t.Length)
}
tw.Flush() // calculate column widths and print table
}
< / code > < / pre >
< p > 为了能按照Artist字段对播放列表进行排序， ， < / p >
< pre > < code class = "language-go" > type byArtist []*Track
func (x byArtist) Len() int { return len(x) }
func (x byArtist) Less(i, j int) bool { return x[i].Artist < x[j].Artist }
func (x byArtist) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
< / code > < / pre >
< p > 为了调用通用的排序程序， ， ： < / p >
< pre > < code class = "language-go" > sort.Sort(byArtist(tracks))
< / code > < / pre >
< p > 在按照artist对这个切片进行排序后， < / p >
< pre > < code > Title Artist Album Year Length
----- ------ ----- ---- ------
Go Ahead Alicia Keys As I Am 2007 4m36s
Go Delilah From the Roots Up 2012 3m38s
Ready 2 Go Martin Solveig Smash 2011 4m24s
Go Moby Moby 1992 3m37s
< / code > < / pre >
< p > 如果用户第二次请求“按照artist排序”， ， < / p >
< pre > < code class = "language-go" > sort.Sort(sort.Reverse(byArtist(tracks)))
< / code > < / pre >
< p > 在按照artist对这个切片进行逆向排序后， < / p >
< pre > < code > Title Artist Album Year Length
----- ------ ----- ---- ------
Go Moby Moby 1992 3m37s
Ready 2 Go Martin Solveig Smash 2011 4m24s
Go Delilah From the Roots Up 2012 3m38s
Go Ahead Alicia Keys As I Am 2007 4m36s
< / code > < / pre >
< p > sort.Reverse函数值得进行更近一步的学习， （ ） ， ， ， < / p >
< pre > < code class = "language-go" > package sort
type reverse struct{ Interface } // that is, sort.Interface
func (r reverse) Less(i, j int) bool { return r.Interface.Less(j, i) }
func Reverse(data Interface) Interface { return reverse{data} }
< / code > < / pre >
< p > reverse的另外两个方法Len和Swap隐式地由原有内嵌的sort.Interface提供。因为reverse是一个不公开的类型， < / p >
< p > 为了可以按照不同的列进行排序， ： < / p >
< pre > < code class = "language-go" > type byYear []*Track
func (x byYear) Len() int { return len(x) }
func (x byYear) Less(i, j int) bool { return x[i].Year < x[j].Year }
func (x byYear) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
< / code > < / pre >
< p > 在使用sort.Sort(byYear(tracks))按照年对tracks进行排序后， ： < / p >
< pre > < code > Title Artist Album Year Length
----- ------ ----- ---- ------
Go Moby Moby 1992 3m37s
Go Ahead Alicia Keys As I Am 2007 4m36s
Ready 2 Go Martin Solveig Smash 2011 4m24s
Go Delilah From the Roots Up 2012 3m38s
< / code > < / pre >
< p > 对于我们需要的每个切片元素类型和每个排序函数， ， ， ， ， ； < / p >
< pre > < code class = "language-go" > type customSort struct {
t []*Track
less func(x, y *Track) bool
}
func (x customSort) Len() int { return len(x.t) }
func (x customSort) Less(i, j int) bool { return x.less(x.t[i], x.t[j]) }
func (x customSort) Swap(i, j int) { x.t[i], x.t[j] = x.t[j], x.t[i] }
< / code > < / pre >
< p > 让我们定义一个多层的排序函数， ， ， ， ： < / p >
< pre > < code class = "language-go" > sort.Sort(customSort{tracks, func(x, y *Track) bool {
if x.Title != y.Title {
return x.Title < y.Title
}
if x.Year != y.Year {
return x.Year < y.Year
}
if x.Length != y.Length {
return x.Length < y.Length
}
return false
}})
< / code > < / pre >
< p > 这下面是排序的结果。注意到两个标题是“Go”的track按照标题排序是相同的顺序， < / p >
< pre > < code > Title Artist Album Year Length
----- ------ ----- ---- ------
Go Moby Moby 1992 3m37s
Go Delilah From the Roots Up 2012 3m38s
Go Ahead Alicia Keys As I Am 2007 4m36s
Ready 2 Go Martin Solveig Smash 2011 4m24s
< / code > < / pre >
< p > 尽管对长度为n的序列排序需要 O(n log n)次比较操作， ， ， ： ： < / p >
< pre > < code class = "language-go" > values := []int{3, 1, 4, 1}
fmt.Println(sort.IntsAreSorted(values)) // " false"
sort.Ints(values)
fmt.Println(values) // " [1 1 3 4]"
fmt.Println(sort.IntsAreSorted(values)) // " true"
sort.Sort(sort.Reverse(sort.IntSlice(values)))
fmt.Println(values) // " [4 3 1 1]"
fmt.Println(sort.IntsAreSorted(values)) // " false"
< / code > < / pre >
< p > 为了使用方便， ， ， ， < / p >
< p > < strong > 练习 7.8： < / strong > 很多图形界面提供了一个有状态的多重排序表格插件： ， ， < / p >
< p > < strong > 练习 7.9： < / strong > 使用html/template包（ ） ， < / p >
< p > < strong > 练习 7.10： < / strong > sort.Interface类型也可以适用在其它地方。编写一个IsPalindrome(s sort.Interface) bool函数表明序列s是否是回文序列， & & !s.Less(j, i)则索引i和j上的元素相等。< / p >
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