Go 语言中排序的 3 种方法-牛翰网

原文链接： Go 语言中排序的 3 种方法

在写代码过程中，排序是经常会遇到的需求，本文会介绍三种常用的方法。

废话不多说，下面正文开始。

使用标准库

根据场景直接使用标准库中的方法，比如：

sort.Ints
sort.Float64s
sort.Strings

举个例子：


s := []int{4, 2, 3, 1}
sort.Ints(s)
fmt.Println(s) // [1 2 3 4]
s := []int{4, 2, 3, 1}
sort.Ints(s)
fmt.Println(s) // [1 2 3 4]
s := []int{4, 2, 3, 1}
sort.Ints(s)
fmt.Println(s) // [1 2 3 4]

自定义比较器

使用 sort.Slice 方法排序时，可以自定义比较函数 less(i, j int) bool，这样就可以根据需要按不同的字段进行排序。

如果想要稳定排序的话，就使用 sort.SliceStable 方法。

举个例子：


family := []struct {
    Name string
    Age  int
}{
    {"Alice", 23},
    {"David", 2},
    {"Eve", 2},
    {"Bob", 25},
}
// Sort by age, keeping original order or equal elements.
sort.SliceStable(family, func(i, j int) bool {
    return family[i].Age < family[j].Age
})
fmt.Println(family) // [{David 2} {Eve 2} {Alice 23} {Bob 25}]
family := []struct {
    Name string
    Age  int
}{
    {"Alice", 23},
    {"David", 2},
    {"Eve", 2},
    {"Bob", 25},
}

// Sort by age, keeping original order or equal elements.
sort.SliceStable(family, func(i, j int) bool {
    return family[i].Age < family[j].Age
})
fmt.Println(family) // [{David 2} {Eve 2} {Alice 23} {Bob 25}]
family := []struct {
    Name string
    Age  int
}{
    {"Alice", 23},
    {"David", 2},
    {"Eve", 2},
    {"Bob", 25},
}

// Sort by age, keeping original order or equal elements.
sort.SliceStable(family, func(i, j int) bool {
    return family[i].Age < family[j].Age
})
fmt.Println(family) // [{David 2} {Eve 2} {Alice 23} {Bob 25}]

自定义数据结构

使用 sort.Sort 或者 sort.Stable 方法，它们可以对任意实现了 sort.Interface 的数据结构排序。


type Interface interface {
    // Len is the number of elements in the collection.
    Len() int
    // Less reports whether the element with
    // index i should sort before the element with index j.
    Less(i, j int) bool
    // Swap swaps the elements with indexes i and j.
    Swap(i, j int)
}
type Interface interface {
    // Len is the number of elements in the collection.
    Len() int
    // Less reports whether the element with
    // index i should sort before the element with index j.
    Less(i, j int) bool
    // Swap swaps the elements with indexes i and j.
    Swap(i, j int)
}
type Interface interface {
    // Len is the number of elements in the collection.
    Len() int
    // Less reports whether the element with
    // index i should sort before the element with index j.
    Less(i, j int) bool
    // Swap swaps the elements with indexes i and j.
    Swap(i, j int)
}

意思就是说，只要某一个数据结构实现了 Len() int，Less(i, j int) bool 和 Swap(i, j int) 这三个方法，那么就可以使用 sort.Sort 来排序。

举个例子：


type Person struct {
    Name string
    Age  int
}
// ByAge implements sort.Interface based on the Age field.
type ByAge []Person
func (a ByAge) Len() int           { return len(a) }
func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
func (a ByAge) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func main() {
    family := []Person{
        {"Alice", 23},
        {"Eve", 2},
        {"Bob", 25},
    }
    sort.Sort(ByAge(family))
    fmt.Println(family) // [{Eve 2} {Alice 23} {Bob 25}]
}
type Person struct {
    Name string
    Age  int
}

// ByAge implements sort.Interface based on the Age field.
type ByAge []Person

func (a ByAge) Len() int           { return len(a) }
func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
func (a ByAge) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

func main() {
    family := []Person{
        {"Alice", 23},
        {"Eve", 2},
        {"Bob", 25},
    }
    sort.Sort(ByAge(family))
    fmt.Println(family) // [{Eve 2} {Alice 23} {Bob 25}]
}
type Person struct {
    Name string
    Age  int
}

// ByAge implements sort.Interface based on the Age field.
type ByAge []Person

func (a ByAge) Len() int           { return len(a) }
func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
func (a ByAge) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

func main() {
    family := []Person{
        {"Alice", 23},
        {"Eve", 2},
        {"Bob", 25},
    }
    sort.Sort(ByAge(family))
    fmt.Println(family) // [{Eve 2} {Alice 23} {Bob 25}]
}

字典排序

我们都知道，字典是无序的，具体原因可以看之前写的这篇文章 Go 语言 map 如何顺序读取？

如果想要字典按 key 或者 value 排序的话，可以这样做。


m := map[string]int{"Alice": 2, "Cecil": 1, "Bob": 3}
keys := make([]string, 0, len(m))
for k := range m {
    keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
    fmt.Println(k, m[k])
}
// Output:
// Alice 2
// Bob 3
// Cecil 1
m := map[string]int{"Alice": 2, "Cecil": 1, "Bob": 3}

keys := make([]string, 0, len(m))
for k := range m {
    keys = append(keys, k)
}
sort.Strings(keys)

for _, k := range keys {
    fmt.Println(k, m[k])
}
// Output:
// Alice 2
// Bob 3
// Cecil 1
m := map[string]int{"Alice": 2, "Cecil": 1, "Bob": 3}

keys := make([]string, 0, len(m))
for k := range m {
    keys = append(keys, k)
}
sort.Strings(keys)

for _, k := range keys {
    fmt.Println(k, m[k])
}
// Output:
// Alice 2
// Bob 3
// Cecil 1