Go language - array

Preface

Array ： A data structure that stores the same data type

The array is a fixed length , How big is defined . Manipulate data in an array , You can operate through indexes .

Create array syntax

Array

var array_name [size]array_type
var array_name = [size]array_type
var array_name = [size]array_type{v1, v2, v3, v4}    // If the value is higher than size Small ,int Type use 0 fill ,string Type is filled with empty string .
var array_name = [size]array_type{index1: v1, index3 : v3} 

//size It's written in ...  The array length will be calculated automatically after the assignment is completed 
array_name := [...]array_type{v1, v2, v3, v4}
array_name := [...]array_type{index1: v1, index3 : v3} 

Multidimensional arrays

One dimensional array ： Storing the data itself

        a1 := [3]int{1,2,3}

Two dimensional array ： What is stored in an array is also an array

        a2 := [3][4]int{ {}, {}, {}}

        Capacity 3 Is the capacity of a two bit array , Store 3 One dimensional array ; Capacity 4 Is the capacity of a one-dimensional array .

func main() {
	arr := [3][4]int{
   {}, {1, 2, 3, 4}, {}}
	fmt.Println(arr)
}

// Output ：[[0 0 0 0] [1 2 3 4] [0 0 0 0]]

Access array

Array

Using the index of an array （ Subscript ） To access the array .

func main() {
	array_test := []int{1, 2, 3, 4}
	fmt.Println(array_test[0], array_test[3])
}

Get the length and capacity of the array ：len() To obtain the length of the 、cap() Capacity acquisition , The length and capacity of the array are equal .

Traversing a two-dimensional array

func main() {
	arr := [2][4]int{
   {}, {1, 2, 3, 4}}
	fmt.Println("--- Array arr---: \n", arr)

	//for loop 
	fmt.Println("\n---for Loop through groups arr---:")
	for i := 0; i < len(arr); i++ {
		for j := 0; j < len(arr[i]); j++ {
			fmt.Printf("%d ", arr[i][j])
		}
	}

	//for range
	fmt.Println("\n---for range Traversal array arr---:")
	for _, arr1val := range arr {
		for _, arr2val := range arr1val {
			fmt.Printf("%d ", arr2val)
		}
	}
}

 

Data type of array

Value type / Reference type

Arrays are value types . When you assign , Copy the original value to the new value . Operating the new value has no effect on the original value .

value type ：int float bool string array

Reference type ：slice map...

Reference type assignment , The new value is the memory address that directly manipulates the original value .

Array Memory analysis

Arrays store data of the same type , Will open up a continuous memory .go Language memory is automatically allocated by the system , When the array is not used , It will be by GC The garbage collection mechanism reclaims from memory .

Address of array , It is actually the address of the first element of the array . Because the element types in the array are the same , Use the same amount of memory . So it's easy to address .

func main() {
	array_test := [4]int{1, 2, 3, 4}
	fmt.Printf("%p-- Array memory address \n", &array_test)
	fmt.Printf("%p-- No 1 Element memory address \n", &array_test[0])
	fmt.Printf("%p-- No 2 Element memory address \n", &array_test[1])
}