go map數據結構

go 聲明(聲明是不會分配內存的，初始化需要make

)
key-value的數據結構，又叫字典或關聯數組:

1. var map1 map[keytype]valuetype
2. var a map[string]string
3. var a map[string]int
4. var a map[int]string
5. var a map[string]map[string]string

map相關操作

package main

import "fmt"


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"] //查找
	if !ok {
		a["zhangsan"] = make(map[string]string)
	}

	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"

	a["key2"] = make(map[string]string)
	a["key2"]["key2"] = "abc"
	a["key2"]["key3"] = "abc"

	trans(a)
	delete(a, "key1")
	fmt.Println("-----")
	trans(a)

	fmt.Println(len(a))
}

func testMap5() {
	var a []map[int]int
	a = make([]map[int]int, 5)
	fmt.Println(a)
	if a[0] == nil {
		a[0] = make(map[int]int)
	}
	a[0][10] = 10
	fmt.Println(a)
}

func main() {

	//testMap2() //map[key1:map[key2:abc key3:abc key4:abc key5:abc]]
	//testMap3() //map[zhangsan:map[nickname:pangpang passwd:123456]]
	testMap4()
	//testMap5()
}

map排序和反轉

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)
	}
	fmt.Println(keys) // [8 3 2 1 18]
	sort.Ints(keys)

	for _, v := range keys {
		fmt.Println(v, a[v])
	}
}

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() {
	// map排序
	testMapSort()
	// map反轉
	testMapSort1() // map[10:efg 101:abc]
}

打印結果:

[8 3 2 1 18]
1 10
2 10
3 10
8 10
18 10
map[10:efg 101:abc]