go map数据结构

map数据结构

key-value的数据结构，又叫字典或关联数组

声明：

var map1 map[keytype]valuetype
var a map[string]string
var a map[string]int
var a map[int]string
var a map[string]map[string]string

备注：声明是不会分配内存的，初始化需要make

样例一：

func testMap() {
var a map[string]string
a = make(map[string]string, 10)
a["abc"] = "efg"
a["abc"] = "efg"
a["abc1"] = "efg"
fmt.Println(a)
}

样例二：

func testMap() {
a := make(map[string]string, 10)
a["abc"] = "efg"
a["abc"] = "efg"
a["abc1"] = "efg"
fmt.Println(a)
}

样例三：

func testMap() {
var a map[string]string = map[string]string{
"key": "value",
}
a["abc"] = "efg"
a["abc"] = "efg"
a["abc1"] = "efg"
fmt.Println(a)
}

map相关操作

var a map[string]string = map[string]string{"hello": "world"}
a = make(map[string]string, 10)

插入和更新：a[“hello”] = “world”

查找：Val, ok := a[“hello”]

遍历：

for k, v := range a {
fmt.Println(k,v)
}

删除：delete(a, “hello”)

长度：len(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))
}

多层map

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)
}

slice of map

func testMapSlice() {
s := make([]map[string]int, 10)
for i := 0; i < len(s); i++ {
s[i] = make(map[string]int, 100)
}
s[0]["abc"] = 100
s[0]["qwe"] = 100
s[5]["abc"] = 100
fmt.Println(s)
}

备注：上面第一次make是切片的长度，第二次make是map的容量

map排序

a. 先获取所有key，把key进行排序

b. 按照排序好的key，进行遍历

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(k, v)
}

sort.Ints(keys)

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

map反转

初始化另外一个map，把key、value互换即可

func test() {
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

fmt.Println(a)

for k, v := range a {
b[v] = k
}

fmt.Println(b)
}