几种常用的排序代码

[toc]

简单的代码

    在我的笔记里面找到几种常用的排序代码，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，我之前是有专门研究的，网上也有很多教程。

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)
}
}
}

使用go自带的排序

对[]int类型排序

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
}

对[]float64类型排序

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
}

对[]string类型排序

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
}

自定义类型排序

    对于自定义类型，需要实现

Less

Swap

Len

sort.Sort

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)
}

便携的用法sort.Slice

    直接使用sort.Slice只需要定义

less func(i, j int) bool

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)

}

便携的用法sort.SliceStable

    该方法类似上一个方法，我看具体实现是使用一个稳定的排序算法。

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)
}

总结

    排序算法是算法的基础，理解算法具体实现有利于锻炼思维，以及通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，通过研究go自带的排序包，发现官方排序会根据数据量将排序分成不同的方式进行，不过最重要的还是快速排序。