# package sort

`import "sort"`

sort包提供了排序切片和用户自定义数据集的函数。

Example

``````package sort_test
import (
"fmt"
"sort"
)
type Person struct {
Name string
Age  int
}
func (p Person) String() string {
return fmt.Sprintf("%s: %d", p.Name, p.Age)
}
// ByAge implements sort.Interface for []Person based on
// the Age field.
type ByAge []Person
func (a ByAge) Len() int           { return len(a) }
func (a ByAge) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
func Example() {
people := []Person{
{"Bob", 31},
{"John", 42},
{"Michael", 17},
{"Jenny", 26},
}
fmt.Println(people)
sort.Sort(ByAge(people))
fmt.Println(people)
// Output:
// [Bob: 31 John: 42 Michael: 17 Jenny: 26]
// [Michael: 17 Jenny: 26 Bob: 31 John: 42]
}
``````

Example (SortKeys)

``````package sort_test
import (
"fmt"
"sort"
)
// A couple of type definitions to make the units clear.
type earthMass float64
type au float64
// A Planet defines the properties of a solar system object.
type Planet struct {
name     string
mass     earthMass
distance au
}
// By is the type of a "less" function that defines the ordering of its Planet arguments.
type By func(p1, p2 *Planet) bool
// Sort is a method on the function type, By, that sorts the argument slice according to the function.
func (by By) Sort(planets []Planet) {
ps := &planetSorter{
planets: planets,
by:      by, // The Sort method's receiver is the function (closure) that defines the sort order.
}
sort.Sort(ps)
}
// planetSorter joins a By function and a slice of Planets to be sorted.
type planetSorter struct {
planets []Planet
by      func(p1, p2 *Planet) bool // Closure used in the Less method.
}
// Len is part of sort.Interface.
func (s *planetSorter) Len() int {
return len(s.planets)
}
// Swap is part of sort.Interface.
func (s *planetSorter) Swap(i, j int) {
s.planets[i], s.planets[j] = s.planets[j], s.planets[i]
}
// Less is part of sort.Interface. It is implemented by calling the "by" closure in the sorter.
func (s *planetSorter) Less(i, j int) bool {
return s.by(&s.planets[i], &s.planets[j])
}
var planets = []Planet{
{"Mercury", 0.055, 0.4},
{"Venus", 0.815, 0.7},
{"Earth", 1.0, 1.0},
{"Mars", 0.107, 1.5},
}
// ExampleSortKeys demonstrates a technique for sorting a struct type using programmable sort criteria.
func Example_sortKeys() {
// Closures that order the Planet structure.
name := func(p1, p2 *Planet) bool {
return p1.name < p2.name
}
mass := func(p1, p2 *Planet) bool {
return p1.mass < p2.mass
}
distance := func(p1, p2 *Planet) bool {
return p1.distance < p2.distance
}
decreasingDistance := func(p1, p2 *Planet) bool {
return !distance(p1, p2)
}
// Sort the planets by the various criteria.
By(name).Sort(planets)
fmt.Println("By name:", planets)
By(mass).Sort(planets)
fmt.Println("By mass:", planets)
By(distance).Sort(planets)
fmt.Println("By distance:", planets)
By(decreasingDistance).Sort(planets)
fmt.Println("By decreasing distance:", planets)
// Output: By name: [{Earth 1 1} {Mars 0.107 1.5} {Mercury 0.055 0.4} {Venus 0.815 0.7}]
// By mass: [{Mercury 0.055 0.4} {Mars 0.107 1.5} {Venus 0.815 0.7} {Earth 1 1}]
// By distance: [{Mercury 0.055 0.4} {Venus 0.815 0.7} {Earth 1 1} {Mars 0.107 1.5}]
// By decreasing distance: [{Mars 0.107 1.5} {Earth 1 1} {Venus 0.815 0.7} {Mercury 0.055 0.4}]
}
``````

Example (SortMultiKeys)

``````package sort_test
import (
"fmt"
"sort"
)
// A Change is a record of source code changes, recording user, language, and delta size.
type Change struct {
user     string
language string
lines    int
}
type lessFunc func(p1, p2 *Change) bool
// multiSorter implements the Sort interface, sorting the changes within.
type multiSorter struct {
changes []Change
less    []lessFunc
}
// Sort sorts the argument slice according to the less functions passed to OrderedBy.
func (ms *multiSorter) Sort(changes []Change) {
ms.changes = changes
sort.Sort(ms)
}
// OrderedBy returns a Sorter that sorts using the less functions, in order.
// Call its Sort method to sort the data.
func OrderedBy(less ...lessFunc) *multiSorter {
return &multiSorter{
less: less,
}
}
// Len is part of sort.Interface.
func (ms *multiSorter) Len() int {
return len(ms.changes)
}
// Swap is part of sort.Interface.
func (ms *multiSorter) Swap(i, j int) {
ms.changes[i], ms.changes[j] = ms.changes[j], ms.changes[i]
}
// Less is part of sort.Interface. It is implemented by looping along the
// less functions until it finds a comparison that is either Less or
// !Less. Note that it can call the less functions twice per call. We
// could change the functions to return -1, 0, 1 and reduce the
// number of calls for greater efficiency: an exercise for the reader.
func (ms *multiSorter) Less(i, j int) bool {
p, q := &ms.changes[i], &ms.changes[j]
// Try all but the last comparison.
var k int
for k = 0; k < len(ms.less)-1; k++ {
less := ms.less[k]
switch {
case less(p, q):
// p < q, so we have a decision.
return true
case less(q, p):
// p > q, so we have a decision.
return false
}
// p == q; try the next comparison.
}
// All comparisons to here said "equal", so just return whatever
// the final comparison reports.
return ms.less[k](p, q)
}
var changes = []Change{
{"gri", "Go", 100},
{"ken", "C", 150},
{"glenda", "Go", 200},
{"rsc", "Go", 200},
{"r", "Go", 100},
{"ken", "Go", 200},
{"dmr", "C", 100},
{"r", "C", 150},
{"gri", "Smalltalk", 80},
}
// ExampleMultiKeys demonstrates a technique for sorting a struct type using different
// sets of multiple fields in the comparison. We chain together "Less" functions, each of
// which compares a single field.
func Example_sortMultiKeys() {
// Closures that order the Change structure.
user := func(c1, c2 *Change) bool {
return c1.user < c2.user
}
language := func(c1, c2 *Change) bool {
return c1.language < c2.language
}
increasingLines := func(c1, c2 *Change) bool {
return c1.lines < c2.lines
}
decreasingLines := func(c1, c2 *Change) bool {
return c1.lines > c2.lines // Note: > orders downwards.
}
// Simple use: Sort by user.
OrderedBy(user).Sort(changes)
fmt.Println("By user:", changes)
// More examples.
OrderedBy(user, increasingLines).Sort(changes)
fmt.Println("By user,<lines:", changes)
OrderedBy(user, decreasingLines).Sort(changes)
fmt.Println("By user,>lines:", changes)
OrderedBy(language, increasingLines).Sort(changes)
fmt.Println("By language,<lines:", changes)
OrderedBy(language, increasingLines, user).Sort(changes)
fmt.Println("By language,<lines,user:", changes)
// Output:
// By user: [{dmr C 100} {glenda Go 200} {gri Smalltalk 80} {gri Go 100} {ken Go 200} {ken C 150} {r Go 100} {r C 150} {rsc Go 200}]
// By user,<lines: [{dmr C 100} {glenda Go 200} {gri Smalltalk 80} {gri Go 100} {ken C 150} {ken Go 200} {r Go 100} {r C 150} {rsc Go 200}]
// By user,>lines: [{dmr C 100} {glenda Go 200} {gri Go 100} {gri Smalltalk 80} {ken Go 200} {ken C 150} {r C 150} {r Go 100} {rsc Go 200}]
// By language,<lines: [{dmr C 100} {ken C 150} {r C 150} {gri Go 100} {r Go 100} {ken Go 200} {glenda Go 200} {rsc Go 200} {gri Smalltalk 80}]
// By language,<lines,user: [{dmr C 100} {ken C 150} {r C 150} {gri Go 100} {r Go 100} {glenda Go 200} {ken Go 200} {rsc Go 200} {gri Smalltalk 80}]
}
``````

Example (SortWrapper)

``````package sort_test
import (
"fmt"
"sort"
)
type Grams int
func (g Grams) String() string { return fmt.Sprintf("%dg", int(g)) }
type Organ struct {
Name   string
Weight Grams
}
type Organs []*Organ
func (s Organs) Len() int      { return len(s) }
func (s Organs) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
// ByName implements sort.Interface by providing Less and using the Len and
// Swap methods of the embedded Organs value.
type ByName struct{ Organs }
func (s ByName) Less(i, j int) bool { return s.Organs[i].Name < s.Organs[j].Name }
// ByWeight implements sort.Interface by providing Less and using the Len and
// Swap methods of the embedded Organs value.
type ByWeight struct{ Organs }
func (s ByWeight) Less(i, j int) bool { return s.Organs[i].Weight < s.Organs[j].Weight }
func Example_sortWrapper() {
s := []*Organ{
{"brain", 1340},
{"heart", 290},
{"liver", 1494},
{"pancreas", 131},
{"prostate", 62},
{"spleen", 162},
}
sort.Sort(ByWeight{s})
fmt.Println("Organs by weight:")
printOrgans(s)
sort.Sort(ByName{s})
fmt.Println("Organs by name:")
printOrgans(s)
// Output:
// Organs by weight:
// prostate (62g)
// pancreas (131g)
// spleen   (162g)
// heart    (290g)
// brain    (1340g)
// liver    (1494g)
// Organs by name:
// brain    (1340g)
// heart    (290g)
// liver    (1494g)
// pancreas (131g)
// prostate (62g)
// spleen   (162g)
}
func printOrgans(s []*Organ) {
for _, o := range s {
fmt.Printf("%-8s (%v)\n", o.Name, o.Weight)
}
}
``````

## type Interface

``````type Interface interface {
// Len方法返回集合中的元素个数
Len() int
// Less方法报告索引i的元素是否比索引j的元素小
Less(i, j int) bool
// Swap方法交换索引i和j的两个元素
Swap(i, j int)
}
``````

## type IntSlice

``````type IntSlice []int
``````

IntSlice给[]int添加方法以满足Interface接口，以便排序为递增序列。

### func (IntSlice) Len

``````func (p IntSlice) Len() int
``````

### func (IntSlice) Less

``````func (p IntSlice) Less(i, j int) bool
``````

### func (IntSlice) Swap

``````func (p IntSlice) Swap(i, j int)
``````

### func (IntSlice) Sort

``````func (p IntSlice) Sort()
``````

Sort等价于调用Sort(p)

``````func (p IntSlice) Search(x int) int
``````

Search等价于调用SearchInts(p, x)

## type Float64Slice

``````type Float64Slice []float64
``````

Float64Slice给[]float64添加方法以满足Interface接口，以便排序为递增序列。

### func (Float64Slice) Len

``````func (p Float64Slice) Len() int
``````

### func (Float64Slice) Less

``````func (p Float64Slice) Less(i, j int) bool
``````

### func (Float64Slice) Swap

``````func (p Float64Slice) Swap(i, j int)
``````

### func (Float64Slice) Sort

``````func (p Float64Slice) Sort()
``````

Sort等价于调用Sort(p)

``````func (p Float64Slice) Search(x float64) int
``````

Search等价于调用SearchFloat64s(p, x)

## type StringSlice

``````type StringSlice []string
``````

StringSlice给[]string添加方法以满足Interface接口，以便排序为递增序列。

### func (StringSlice) Len

``````func (p StringSlice) Len() int
``````

### func (StringSlice) Less

``````func (p StringSlice) Less(i, j int) bool
``````

### func (StringSlice) Swap

``````func (p StringSlice) Swap(i, j int)
``````

### func (StringSlice) Sort

``````func (p StringSlice) Sort()
``````

Sort等价于调用Sort(p)

``````func (p StringSlice) Search(x string) int
``````

Search等价于调用SearchStrings(p, x)

## func Sort

``````func Sort(data Interface)
``````

Sort排序data。它调用1次data.Len确定长度，调用O(n*log(n))次data.Less和data.Swap。本函数不能保证排序的稳定性（即不保证相等元素的相对次序不变）。

## func Stable

``````func Stable(data Interface)
``````

Stable排序data，并保证排序的稳定性，相等元素的相对次序不变。

## func IsSorted

``````func IsSorted(data Interface) bool
``````

IsSorted报告data是否已经被排序。

## func Reverse

``````func Reverse(data Interface) Interface
``````

Reverse包装一个Interface接口并返回一个新的Interface接口，对该接口排序可生成递减序列。

Example

``````s := []int{5, 2, 6, 3, 1, 4} // unsorted
sort.Sort(sort.Reverse(sort.IntSlice(s)))
fmt.Println(s)
``````

Output:

``````[6 5 4 3 2 1]
``````
``````func Search(n int, f func(int) bool) int
``````

Search函数采用二分法搜索找到[0, n)区间内最小的满足f(i)==true的值i。也就是说，Search函数希望f在输入位于区间[0, n)的前面某部分（可以为空）时返回假，而在输入位于剩余至结尾的部分（可以为空）时返回真；Search函数会返回满足f(i)==true的最小值i。如果没有该值，函数会返回n。注意，未找到时的返回值不是-1，这一点和strings.Index等函数不同。Search函数只会用区间[0, n)内的值调用f。

``````x := 23
i := sort.Search(len(data), func(i int) bool { return data[i] >= x })
if i < len(data) && data[i] == x {
// x is present at data[i]
} else {
// x is not present in data,
// but i is the index where it would be inserted.
}
``````

``````func GuessingGame() {
var s string
fmt.Printf("Pick an integer from 0 to 100.\n")
answer := sort.Search(100, func(i int) bool {
fmt.Printf("Is your number <= %d? ", i)
fmt.Scanf("%s", &s)
return s != "" && s[0] == 'y'
})
}
``````

## func Ints

``````func Ints(a []int)
``````

Ints函数将a排序为递增顺序。

Example

``````s := []int{5, 2, 6, 3, 1, 4} // unsorted
sort.Ints(s)
fmt.Println(s)
``````

Output:

``````[1 2 3 4 5 6]
``````

## func IntsAreSorted

``````func IntsAreSorted(a []int) bool
``````

IntsAreSorted检查a是否已排序为递增顺序。

## func SearchInts

``````func SearchInts(a []int, x int) int
``````

SearchInts在递增顺序的a中搜索x，返回x的索引。如果查找不到，返回值是x应该插入a的位置（以保证a的递增顺序），返回值可以是len(a)。

## func Float64s

``````func Float64s(a []float64)
``````

Float64s函数将a排序为递增顺序。

## func Float64sAreSorted

``````func Float64sAreSorted(a []float64) bool
``````

Float64sAreSorted检查a是否已排序为递增顺序。

## func SearchFloat64s

``````func SearchFloat64s(a []float64, x float64) int
``````

SearchFloat64s在递增顺序的a中搜索x，返回x的索引。如果查找不到，返回值是x应该插入a的位置（以保证a的递增顺序），返回值可以是len(a)。

## func Strings

``````func Strings(a []string)
``````

Strings函数将a排序为递增顺序。

## func StringsAreSorted

``````func StringsAreSorted(a []string) bool
``````

StringsAreSorted检查a是否已排序为递增顺序。

## func SearchStrings

``````func SearchStrings(a []string, x string) int
``````

SearchStrings在递增顺序的a中搜索x，返回x的索引。如果查找不到，返回值是x应该插入a的位置（以保证a的递增顺序），返回值可以是len(a)。