map數據結構

key-value的數據結構，又叫字典或關聯數組

• 聲明：

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

備注：聲明是不會分配內存的，初始化需要make

樣例一：

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

樣例二：

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

樣例三：

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

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• map相關操作

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”]

遍歷：

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

刪除：delete(a, “hello”)

長度：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)) }

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• 多層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) }

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• 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) }

備注：上面第一次make是切片的長度，第二次make是map的容量

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• map排序

a.?先獲取所有key，把key進行排序

b. 按照排序好的key，進行遍歷

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])} }

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• map反轉

初始化另外一個map，把key、value互換即可

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) }

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轉載于:https://www.cnblogs.com/shhnwangjian/p/7446995.html

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