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]stringa = 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"] = 100s[0]["qwe"] = 100s[5]["abc"] = 100fmt.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]inta = make(map[int]int, 5)a[8] = 10a[3] = 10a[2] = 10a[1] = 10a[18] = 10var keys []intfor 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]intvar b map[int]stringa = make(map[string]int, 5)b = make(map[int]string, 5)a["abc"] = 101a["efg"] = 10fmt.Println(a)for k, v := range a {b[v] = k}fmt.Println(b)
}
