map数据结构

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// map实例-1 声明一个map并初始化-1
func testMap1() {var a map[string]string         //声明一个mapa = make(map[string]string, 10) //初始化，申请内存空间a["abc"] = "efg"a["abc2"] = "efg44"fmt.Println(a)
}// map实例-2 声明一个map并初始化-2
func testMap2() {var a map[string]string = map[string]string{"key": "value",} //声明一个map,并且初始化a["abc"] = "efg"a["abc2"] = "efg44"fmt.Println(a)
}

  //声明一个mapvar m1 map[string]intfmt.Println(m1 == nil) //还没有初始化，就没有内存空间的开辟//初始化mapm1 = make(map[string]int, 10) //申请map的大小//map增加和更新值m1["lqx"] = 20m1["刘"] = 21m1["lqx"] = 18fmt.Println(m1) //map[lqx:18 刘:21]//判断是否存在一个值fmt.Println(m1["lll"]) //如果没有值，会返回一个默认值v, ok := m1["lll"]     //如果不存在，ok会返回falsefmt.Println(v, ok)//长度fmt.Println(len(m1))//遍历mapfor i, v := range m1 {fmt.Println(i, v)}// delete()函数删除键值对delete(m1, "lqc") //如果没有，就忽略delete(m1, "lqx")fmt.Println(m1)

// map实例-3 map嵌套
func testMap3() {a := make(map[string]map[string]string, 100) //声明一个map，并初始化，指定大小为100a["key1"] = make(map[string]string)          //初始化map里面的mapa["key1"]["key2"] = "abc"a["key1"]["key3"] = "abc"fmt.Println(a)
}// map实例-4 判断map值,查找，添加，修改
func modify(a map[string]map[string]string) {_, ok := a["zhangsan"]if !ok {a["zhangsan"] = make(map[string]string)}a["zhangsan"]["password"] = "123456"a["zhangsan"]["nickname"] = "pangpang"return
}
func testmap4() {a := make(map[string]map[string]string, 100)modify(a)fmt.Println(a)
}// map实例－５　遍历map,删除，计算长度
func testmap5() {a := make(map[string]map[string]string, 100) //声明一个map，并初始化，指定大小为100a["key1"] = make(map[string]string)          //初始化map里面的mapa["key1"]["key2"] = "abc"a["key1"]["key3"] = "abc"a["key1"]["key4"] = "abc"a["key1"]["key5"] = "abc"a["key2"] = make(map[string]string) //初始化map里面的mapa["key2"]["key1"] = "abc"a["key2"]["key2"] = "abc"a["key2"]["key3"] = "abc"for k, v := range a {fmt.Println(k)for k1, v1 := range v {fmt.Println("\t", k1, v1)}}

func testmap6() {// var a = make([]map[int]int, 5) //等同于下面的写法var a []map[int]inta = make([]map[int]int, 5)for i := 0; i < 5; i++ {a[i] = make(map[int]int)}a[0][10] = 100fmt.Println(a) //[map[10:100] map[] map[] map[] map[]]
}

func testmapsort() {// var a = make([]map[int]int, 5) //等同于下面的写法var a map[int]inta = make(map[int]int, 5)a[0] = 1003a[12] = 1012311a[11] = 1012123a[10] = 103123a[1] = 1012222a[3] = 10121a[5] = 10123fmt.Println(a) //map[0:1003 1:1012222 3:10121 5:10123 10:103123 11:1012123 12:1012311]
}

func testmapsort1() {var a map[string]intvar b map[int]stringa = make(map[string]int, 5)b = make(map[int]string, 5)a["abc"] = 101a["ccc"] = 1123123for k, v := range a {b[v] = k}fmt.Println(a, "\t", b)
}