在个人笔记里面找到几种经常使用的排序代码，包括“冒泡排序、选择排序、二分排序、快速排序”。关于这些排序的原理，我以前是有专门研究的，网上也有不少教程。算法
package main
import (
"fmt"
"math/rand"
"time"
)
func main() {
rand.Seed(time.Now().Unix())
s := randInt(20)
BubblingSort(s, len(s))
fmt.Println(s)
s = randInt(20)
SelectSort(s, len(s))
fmt.Println(s)
s = randInt(20)
BisectionSort(s, len(s))
fmt.Println(s)
s = randInt(20)
quickSort(s, 0, len(s)-1)
fmt.Println(s)
}
func randInt(n int) []int {
res := make([]int, n)
for i := 0; i < n; i++ {
res[i] = rand.Intn(100)
}
return res
}
func BubblingSort(nums []int, ln int) {
for i := 0; i < ln-1; i++ {
flag := true
for j := 0; j < ln-i-1; j++ {
if nums[j] > nums[j+1] {
nums[j], nums[j+1] = nums[j+1], nums[j]
flag = false
}
}
if flag {
break // 已经有序,不用继续
}
}
}
func SelectSort(nums []int, ln int) {
for i := 0; i < ln; i++ {
min := i
for j := i + 1; j < ln; j++ {
if nums[min] > nums[j] {
min = j
}
}
nums[i], nums[min] = nums[min], nums[i]
}
}
func BisectionSort(nums []int, ln int) {
for i := 1; i < ln; i++ {
tmp := nums[i]
low, mid, high := 0, -1, i-1
for low <= high {
mid = (low + high) / 2
if tmp < nums[mid] {
high = mid - 1
} else {
low = mid + 1
}
}
for j := i - 1; j >= low; j-- {
nums[j+1] = nums[j]
}
if low != i {
nums[low] = tmp
}
}
}
func quickSort(num []int, low, high int) {
s, e, k := low, high, num[low]
for e > s {
for e > s && num[e] >= k {
e--
}
if num[e] <= k {
num[s], num[e] = num[e], num[s]
}
for e > s && num[s] <= k {
s++
}
if num[s] >= k {
num[s], num[e] = num[e], num[s]
}
if s > low {
quickSort(num, low, s-1)
}
if e < high {
quickSort(num, e+1, high)
}
}
}
package main
import (
"fmt"
"math/rand"
"sort"
"time"
)
func main() {
rand.Seed(time.Now().Unix())
s := randInt(20)
sort.Ints(s)
fmt.Println(s)
}
func randInt(n int) []int {
res := make([]int, n)
for i := 0; i < n; i++ {
res[i] = rand.Intn(100)
}
return res
}
package main
import (
"fmt"
"math/rand"
"sort"
"time"
)
func main() {
rand.Seed(time.Now().Unix())
s := randFloat64(20)
sort.Float64s(s)
fmt.Println(s)
}
func randFloat64(n int) []float64 {
res := make([]float64, n)
for i := 0; i < n; i++ {
res[i] = rand.Float64()
}
return res
}
package main
import (
"encoding/base64"
"fmt"
"math/rand"
"sort"
"time"
)
func main() {
rand.Seed(time.Now().Unix())
s := randString(20)
sort.Strings(s)
fmt.Println(s)
}
func randString(n int) []string {
res := make([]string, n)
tmp := make([]byte, 10)
for i := 0; i < n; i++ {
rand.Read(tmp)
res[i] = base64.StdEncoding.EncodeToString(tmp)
}
return res
}
对于自定义类型，须要实现Less、Swap、Len这三个sort包的接口，而后直接使用sort.Sort方法就能够了。less
package main
import (
"encoding/base64"
"fmt"
"math/rand"
"sort"
)
func main() {
peoples := SortPeople{
{
name: "张三",
age: 25,
}, {
name: "李四",
age: 18,
}, {
name: "王五",
age: 20,
},
}
sort.Sort(peoples)
fmt.Println(peoples)
}
type (
people struct {
name string
age int
}
SortPeople []people
)
func (d SortPeople) Less(i, j int) bool {
return d[i].age < d[j].age
}
func (d SortPeople) Swap(i, j int) {
d[i], d[j] = d[j], d[i]
}
func (d SortPeople) Len() int {
return len(d)
}
直接使用sort.Slice只须要定义less func(i, j int) bool方法就能够完成排序，代码是经过快速排序完成，不过具体实现加了反射，性能稍微有影响。性能
package main
import (
"encoding/base64"
"fmt"
"math/rand"
"sort"
)
func main() {
peoples := []people{
{
name: "张三",
age: 25,
}, {
name: "李四",
age: 18,
}, {
name: "王五",
age: 20,
},
}
sort.Slice(peoples, func(i, j int) bool {
return peoples[i].age < peoples[j].age
})
fmt.Println(peoples)
}
该方法相似上一个方法，我看具体实现是使用一个稳定的排序算法。ui
package main
import (
"encoding/base64"
"fmt"
"math/rand"
"sort"
)
func main() {
peoples := []people{
{
name: "张三",
age: 25,
}, {
name: "李四",
age: 18,
}, {
name: "王五",
age: 20,
},
}
sort.SliceStable(peoples, func(i, j int) bool {
return peoples[i].age < peoples[j].age
})
fmt.Println(peoples)
}
排序算法是算法的基础，理解算法具体实现有利于锻炼思惟，以及经过分析排序的优缺点，在合适的时候使用合适的排序方法。最重要的是高效和节省资源的平衡，经过研究go自带的排序包，发现官方排序会根据数据量将排序分红不一样的方式进行，不过最重要的仍是快速排序。code