3.1. Array
(1) Definition of the array
main Package
Import (
"FMT"
)
FUNC main () {
// define an array can not use var initial value
var of arr1 [. 5] // int [0 0 0 0 0]
// initial value must be specified by colons
arr2: = [. 3] {l, 3,5} // int [. 1. 3. 5]
// with "..." denotes any number
arr3: = [...] int { 2,4,6,8,10} // [2. 8. 6 10. 4]
fmt.Println (of arr1, arr2 is, ARR3)
}
Traversing (2) of the array
With the range keyword
main Package
Import (
"FMT"
)
FUNC main () {
ARR3: = [...] {2,4,6,8,10} // int [2. 8. 6 10. 4]
fmt.Println (ARR3)
// array traversal
for I: = {Range ARR3
fmt.Println (ARR3 [I])
}
}
// results
2
. 4
. 6
. 8
10
Acquiring index and value
main Package
Import (
"FMT"
)
FUNC main () {
ARR3: = [...] {2,4,6,8,10} // int [2. 8. 6 10. 4]
fmt.Println (ARR3)
// array traversal
for I, V: = Range ARR3 {
fmt.Println (I, V)
}
}
// results
0 2
. 1. 4
2. 6
. 3. 8
. 4 10
(3) is a value type array
- [10] int and [20] int different types
- Call func f (arr [10] int) will be copied array
- Generally not used in an array of languages go, while using slices
package main
import (
"fmt"
)
func printArray(arr [5]int){
for i ,v:= range arr{
fmt.Println(i,v)
}
}
func main() {
//arr2 := [3]int{1,3,5}
arr3 := [...]int{2,4,6,8,10}
printArray(arr3)
}
//结果
0 2
1 4
2 6
3 8
4 10
If the error pass arr2
package main
import (
"fmt"
)
func printArray(arr [5]int){
for i ,v:= range arr{
fmt.Println(i,v)
}
}
func main() {
arr2 := [3]int{1,3,5}
//arr3 := [...]int{2,4,6,8,10}
printArray(arr2) //cannot use arr2 (type [3]int) as type [5]int in argument to printArray
}
3.2. Slice
(1) sliced
package main
import "fmt"
func main() {
arr := [...]int{0,1,2,3,4,5,6,7}
fmt.Println(arr[2:6]) //[2 3 4 5]
fmt.Println(arr[:6]) //[0 1 2 3 4 5]
fmt.Println(arr[2:]) //[2 3 4 5 6 7]
fmt.Println(arr[:]) //[0 1 2 3 4 5 6 7]
}
(2) slice extension
slice can be extended backward, not forward extension
package main
import "fmt"
func main() {
arr := [...]int{0,1,2,3,4,5,6,7}
s1 := arr[2:6]
s2 := s1[3:5]
fmt.Println(s1) //[2 3 4 5]
fmt.Println(s2) //[5 6]
}
How s2 is accessible to [5,6] of
Implement (3) slice of
slice the bottom three hidden value
s [i] may not exceed len (s), it may not extend rearwardly beyond the underlying array cap (s)
package main
import "fmt"
func main() {
arr := [...]int{0,1,2,3,4,5,6,7}
s1 := arr[2:6]
s2 := s1[3:5]
fmt.Println("arr = ",arr) //arr = [0 1 2 3 4 5 6 7]
fmt.Printf("s1=%v,len(s1)=%d,cap(s1)=%d\n",s1,len(s1),cap(s1)) //s1=[2 3 4 5],len(s1)=4,cap(s1)=6
fmt.Printf("s2=%v,len(s2)=%d,cap(s2)=%d\n",s2,len(s2),cap(s2)) //s2=[5 6],len(s2)=2,cap(s2)=3
fmt.Println(s1[3:6]) //[5 6 7]
}
3.3.切片的操作
（1）向slice添加元素
- 添加元素时，如果超出了cap，系统会重新分配更大的底层数组
- 由于值传递的关系，必须接收append的返回值。s = append(s,val)
package main
import "fmt"
func main() {
arr := [...]int{0,1,2,3,4,5,6,7}
s1 := arr[2:6] //[2 3 4 5]
s2 := s1[3:5] //[5 6]
s3 := append(s2,10)
s4 := append(s3,11)
s5 := append(s4,12)
fmt.Println(s3,s4,s5) //[5 6 10] [5 6 10 11] [5 6 10 11 12]
//因为s2的cap是[5,6,7],s3 append把7替换成10，s4后超出了cap
fmt.Println(arr) //[0 1 2 3 4 5 6 10]
}
（2）slice的创建
package main
import "fmt"
func main() {
//第一种
//Zero value for slice is nil
var s1 []int
fmt.Println(s1) //[]
for i := 0; i < 5 ; i++{
s1 = append(s1,i)
}
fmt.Println(s1) //[0 1 2 3 4]
//第二种
s2 := []int{2,4,6,8}
fmt.Printf("len(s2)=%d,cap(s2)=%d\n",len(s2),cap(s2)) //len(s2)=4,cap(s2)=4
//第三种
s3 := make([]int,16)
fmt.Printf("len(s3)=%d,cap(s3)=%d\n",len(s3),cap(s3)) //len(s3)=16,cap(s3)=16
//第四种
s4 := make([]int,16,32)
fmt.Printf("len(s4)=%d,cap(s4)=%d\n",len(s4),cap(s4)) //len(s4)=16,cap(s4)=32
}
（3）slice的删除
package main
import "fmt"
func main() {
s1 := []int{0,1,2,3,4,5,6}
fmt.Println(s1) //[0 1 2 3 4 5 6]
//删除index为3的值
s1 = append(s1[:3],s1[4:]...)
fmt.Println(s1) //[0 1 2 4 5 6]
}