Golang Basic--map Dictionary

Map similar to Dict (dictionary type) in Python language to store data in key-value form

• Key must be a == ！= type that supports or compares operations, and cannot be a function, map, or slice
• Map lookup is much faster than linear search, but 100 times times slower than using indexed access data

• Map uses the make () function to create := a simple notation that supports assignment

  //基本操作func main() {    var m map[int]string //定义一个map变量    m = map[int]string{}        //第一种方式    m = make(map[int]string)  //第二种方式：使用make    m := make(map[int]string) //第三种方式make直接初始化    m[1] = "ok"               //赋值一对key-value    a := m[1]                 //获取一个key对应的value值    delete(m, 1)              //删除map中的某一个key            fmt.Println(m)    fmt.Println(m)    fmt.Println(a)    fmt.Println(m)}/*outputmap_init---->   map[]map_add---->    map[1:ok]map_get---->    okmap_del---->    map[]*/

Nested map: A nested dictionary similar to Python, with values that require layers of progression when assigned, and the need to perform make initialization on the inner map each time you assign a value.

• Sample code

  package mainimport "fmt"func main() {    var m map[int]map[int]string     //嵌套字典    m = make(map[int]map[int]string) //初始化map--最外层    m[1] = make(map[int]string)      //make初始化嵌套字典，第一个键对应的map类型    m[1][1] = "ok"                   //key1_value1赋值    b, ok := m[1][1]                 //使用多返回值，第二值返回值时bool类型，如果前一个有返回值，返回true,反之返回false    fmt.Println(b, ok)    fmt.Println(m)    a, ok := m[2][1] //由于key2，对应的value2赋值前没有make初始化，所以，    fmt.Println(a, ok)    if !ok {        m[2] = make(map[int]string)    }    m[2][1] = "Good"    a, ok = m[2][1]    fmt.Println(a, ok)    fmt.Println(m)}/*输出a, ok--->   ok truem --->      map[1:map[1:ok]]a, ok--->        falsea, ok--->   Good true           //初始化后*/

For iterative operations, similar to the python,dict operation, for K,v in DIC.

• Sample code

  //for 迭代操作slicepackage mainimport "fmt"func main() {    sum := make([]map[int]string, 5) //初始化一个slice,元素是map类型    for i := range sum {        sum[i] = make(map[int]string, 1)        sum[i][1] = "ok"        fmt.Println(sum[i])    }    fmt.Println(sum)}/*输出i=0--->     map[1:ok]i=1--->     map[1:ok]i=2--->     map[1:ok]i=3--->     map[1:ok]i=4--->     map[1:ok]sum--->     [map[1:ok] map[1:ok] map[1:ok] map[1:ok] map[1:ok]]*/

Map, indirect sort, by slice, the key is sorted.

• Sample code

  //间接排序,对key进行排序package mainimport "fmt"import "sort" //排序包func main() {    m := map[int]string{1: "a", 2: "b", 3: "c", 4: "d"}    //这是一个map类型    s := make([]int, len(m))                                        //这是一个slice类型    i := 0    for k := range m {        s[i] = k        i ++    }    sort.Ints(s)    fmt.Println(s)}/*输出[1 2 3 4]*/