目录

Go - Slice

Go Slice是Go Array的抽象。 Go Array允许您定义可以包含多个同类数据项的变量,但它不提供任何内置方法来动态增加其大小或获取自己的子数组。 切片克服了这个限制。 它提供了Array所需的许多实用功能,并广泛用于Go编程。

定义切片

要定义切片,可以将其声明为数组而不指定其大小。 或者,您可以使用make函数创建切片。

var numbers []int /* a slice of unspecified size */
/* numbers == []int{0,0,0,0,0}*/
numbers = make([]int,5,5) /* a slice of length 5 and capacity 5*/

len() and cap() 函数

切片是数组的抽象。 它实际上使用数组作为底层结构。 len()函数返回切片中的元素,其中cap()函数返回切片的容量(即,它可以容纳多少元素)。 以下示例解释了切片的用法 -

package main
import "fmt"
func main() {
   var numbers = make([]int,3,5)
   printSlice(numbers)
}
func printSlice(x []int){
   fmt.Printf("len=%d cap=%d slice=%v\n",len(x),cap(x),x)
}

编译并执行上述代码时,会产生以下结果 -

len = 3 cap = 5 slice = [0 0 0]

零切片

如果声明切片没有输入,则默认情况下,它被初始化为nil。 它的长度和容量为零。 例如 -

package main
import "fmt"
func main() {
   var numbers []int
   printSlice(numbers)
   if(numbers == nil){
      fmt.Printf("slice is nil")
   }
}
func printSlice(x []int){
   fmt.Printf("len = %d cap = %d slice = %v\n", len(x), cap(x),x)
}

编译并执行上述代码时,会产生以下结果 -

len = 0 cap = 0 slice = []
slice is nil

Subslicing

Slice允许使用[lower-bound:upper-bound]指定下限和上限来获取它的子切片。 例如 -

package main
import "fmt"
func main() {
   /* create a slice */
   numbers := []int{0,1,2,3,4,5,6,7,8}   
   printSlice(numbers)
   /* print the original slice */
   fmt.Println("numbers ==", numbers)
   /* print the sub slice starting from index 1(included) to index 4(excluded)*/
   fmt.Println("numbers[1:4] ==", numbers[1:4])
   /* missing lower bound implies 0*/
   fmt.Println("numbers[:3] ==", numbers[:3])
   /* missing upper bound implies len(s)*/
   fmt.Println("numbers[4:] ==", numbers[4:])
   numbers1 := make([]int,0,5)
   printSlice(numbers1)
   /* print the sub slice starting from index 0(included) to index 2(excluded) */
   number2 := numbers[:2]
   printSlice(number2)
   /* print the sub slice starting from index 2(included) to index 5(excluded) */
   number3 := numbers[2:5]
   printSlice(number3)
}
func printSlice(x []int){
   fmt.Printf("len = %d cap = %d slice = %v\n", len(x), cap(x),x)
}

编译并执行上述代码时,会产生以下结果 -

len = 9 cap = 9 slice = [0 1 2 3 4 5 6 7 8]
numbers == [0 1 2 3 4 5 6 7 8]
numbers[1:4] == [1 2 3]
numbers[:3] == [0 1 2]
numbers[4:] == [4 5 6 7 8]
len = 0 cap = 5 slice = []
len = 2 cap = 9  slice = [0 1]
len = 3 cap = 7 slice = [2 3 4]

append() and copy() 函数

可以使用append()函数增加切片的容量。 使用copy()函数,源片的内容将复制到目标片。 例如 -

package main
import "fmt"
func main() {
   var numbers []int
   printSlice(numbers)
   /* append allows nil slice */
   numbers = append(numbers, 0)
   printSlice(numbers)
   /* add one element to slice*/
   numbers = append(numbers, 1)
   printSlice(numbers)
   /* add more than one element at a time*/
   numbers = append(numbers, 2,3,4)
   printSlice(numbers)
   /* create a slice numbers1 with double the capacity of earlier slice*/
   numbers1 := make([]int, len(numbers), (cap(numbers))*2)
   /* copy content of numbers to numbers1 */
   copy(numbers1,numbers)
   printSlice(numbers1)   
}
func printSlice(x []int){
   fmt.Printf("len=%d cap=%d slice=%v\n",len(x),cap(x),x)
}

编译并执行上述代码时,会产生以下结果 -

len = 0 cap = 0 slice = []
len = 1 cap = 2 slice = [0]
len = 2 cap = 2 slice = [0 1]
len = 5 cap = 8 slice = [0 1 2 3 4]
len = 5 cap = 16 slice = [0 1 2 3 4]
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