排序&二分查找

package main

import (
    "fmt"
    "sort"
)

var nums = []int{6, 42, 45, 81, 85, 42, 40, 57, 8, 1}
var cs = []string{"HA", "mmo0", "shSEpJ", "4C", "DKaHg", "B", "KI", "G", "Pnf", "2k8eQ"}
var persons = []Person{{"zeng qiang", 28}, {"xiao ming", 18}, {"yu wei", 36}}

func main() {
    sort.Ints(nums) // 升序
    fmt.Println("nums asc", nums)

    keyword1 := 57
    i := sort.SearchInts(nums, 57) // 二分法查找元素(仅升序)
    fmt.Println(keyword1, "in", i)
    sort.Sort(sort.Reverse(sort.IntSlice(nums))) // 降序
    fmt.Println("nums desc", nums)

    fmt.Println()

    sort.Strings(cs) // 升序
    fmt.Println("cs asc", cs)
    keyword2 := "4C"
    i = sort.SearchStrings(cs, keyword2)
    fmt.Println(keyword2, "in", i)
    sort.SliceStable(cs, func(i, j int) bool { // 按字符串最后一个字符升序
        return cs[i][len(cs[i])-1] < cs[j][len(cs[j])-1]
    })
    fmt.Println(cs)

    fmt.Println()

    sort.SliceStable(persons, func(i, j int) bool { // 结构体按年龄升序
        return persons[i].Age < persons[j].Age
    })
    fmt.Println("persons age asc", persons)

    age := 28                                                                        // 按年龄查询下标
    i = sort.Search(len(persons), func(i int) bool { return persons[i].Age >= age }) // 二分查找结构体
    fmt.Println(age, "in", i)

    sort.SliceStable(persons, func(i, j int) bool { // 结构体按名称(字符串)升序
        return persons[i].Name < persons[j].Name
    })
    fmt.Println("persons name asc", persons)

    name := "zeng qiang"                                                               // 按名字(字符串)查询下标
    i = sort.Search(len(persons), func(i int) bool { return persons[i].Name >= name }) // 二分查找结构体
    fmt.Println(name, "in", i)

}

type Person struct {
    Name string `json:"name"`
    Age  int    `json:"age"`
}

生成数组

在线1：https://play.golang.org/
在线2：https://play.studygolang.com/

package main

import (
    "encoding/json"
    "fmt"
    "math/rand"
    "strings"
    "time"
)

//在线1：https://play.golang.org/
//在线2：https://play.studygolang.com/

func init() {
    t := time.Now().UnixNano()
    rand.Seed(t)
}

func main() {
    ints(10)  // 生成整数数组
    chars(10) // 生成字符串数组
}

func ints(length int) {
    if length <= 0 {
        length = 10
    }

    var arr []int
    for i := 0; i < length; i++ {
        arr = append(arr, rand.Intn(100))
    }
    s, _ := json.Marshal(arr)
    nums := strings.Trim(string(s), "[]")
    fmt.Printf("%s{%s}\n", "var arr = []int", nums)
}

func chars(length int) {

    if length <= 0 {
        length = 10
    }
    var arr []string
    for i := 0; i < length; i++ {
        l := 1
        t := rand.Intn(6)
        if t > 0 {
            l = t
        }
        arr = append(arr, monoStr(l))
    }

    for i := 0; i < len(arr); i++ {
        arr[i] = fmt.Sprintf("\"%s\"", arr[i])
    }
    fmt.Printf("%s{%s}\n", "var chars = []string", strings.Join(arr, ","))
}

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
const (
    letterIdxBits = 6                    // 6 bits to represent a letter index
    letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
    letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

var src = rand.NewSource(time.Now().UnixNano())

func monoStr(n int) string {

    b := make([]byte, n)
    for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
        if remain == 0 {
            cache, remain = src.Int63(), letterIdxMax
        }
        if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
            b[i] = letterBytes[idx]
            i--
        }
        cache >>= letterIdxBits
        remain--
    }
    return string(b)
}