golang之map数据类型

package main

import "fmt"

func testMap() {
    //两种声明map方式，切记，必须初始化才能用，否则panic

    //var a map[string]string = map[string]string{
    //    "key": "value",
    //}
    a := make(map[string]string, 10)
    a["abc"] = "efg"
    //map的key是唯一的，修改值可以直接改
    a["abc"] = "efg2"
    a["abc1"] = "efg"
    fmt.Println(a)
}

//map嵌套map
//map是无序排序
func testMap2() {
    a := make(map[string]map[string]string, 100)
    a["key1"] = make(map[string]string)
    a["key1"]["key2"] = "abc"
    a["key1"]["key3"] = "abc"
    a["key1"]["key4"] = "abc"
    a["key1"]["key5"] = "abc"
    fmt.Println(a)
}

func modify(a map[string]map[string]string) {
    _, ok := a["zhangsan"]
    if !ok {
        a["zhangsan"] = make(map[string]string)
    }
    //与_,ok写法一样
    //if a["zhangsan"] == nil {}
    //
    a["zhangsan"]["passwd"] = "123456"
    a["zhangsan"]["nickname"] = "pangpang"
    return
}

func testMap3() {
    a := make(map[string]map[string]string, 100)
    modify(a)
    fmt.Println(a)
}
func trans(a map[string]map[string]string) {
    for k, v := range a {
        fmt.Println(k)
        for k1, v1 := range v {
            fmt.Println("\t", k1, v1)
        }
    }
}
func testMap4() {
    a := make(map[string]map[string]string, 100)
    a["key1"] = make(map[string]string)
    a["key1"]["key2"] = "abc"
    a["key1"]["key3"] = "abc"
    a["key1"]["key4"] = "abc"
    a["key1"]["key5"] = "abc"
    //删除map键的内置函数delete
    //delete(a,"key1")
    trans(a)

    fmt.Println(len(a))

}

func testMap5() {
    var a []map[int]int
    a = make([]map[int]int, 5)

    //for i:=0;i<5;i++{}

    //map,slice判断空是nil
    if a[0] == nil {
        a[0] = make(map[int]int)
    }
    a[0][10] = 10
    fmt.Println(a)
}

func main() {
    testMap()
    testMap2()
    testMap3()
    testMap4()
    testMap5()
}

package main

import (
    "fmt"
    "sort"
)

func testMapSort() {
    var a map[int]int
    a = make(map[int]int, 5)
    a[8] = 10
    a[3] = 10
    a[2] = 10
    a[1] = 10
    a[18] = 10
    var keys []int
    for k, _ := range a {
        keys = append(keys, k)

    }
    sort.Ints(keys)
    for _, v := range keys {
        fmt.Println(v, a[v])
    }
}
//map反转
func testMapSort1() {
    var a map[string]int
    var b map[int]string
    a = make(map[string]int, 5)
    b = make(map[int]string, 5)
    a["abc"] = 101
    a["efg"] = 10
    for k, v := range a {
        b[v] = k
    }
    fmt.Println(b)
}
func main() {
    //testMapSort()
    testMapSort1()
}