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(" ", 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)
}
