Golang Slicing Slice

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Sliced slice

• It is not an array by itself, it points to the underlying array

package mainimport (    "fmt")func main() {    var s1 []int //这样的话就完成了slice的声明，如果是数组的话，必须在中括号当中必须有明确的数字或3个点    fmt.Println(s1)}

• As an alternative to arrays, you can associate local or all of the underlying array

package mainimport (    "fmt")func main() {    var s1 []int //这样的话就完成了slice的声明，如果是数组的话，必须在中括号当中必须有明确的数字或3个点，这是个空slice    a := [10]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}    fmt.Println(s1)    fmt.Println(a)    s2 := a[9]    s3 := a[5:10] //a[5,6,7,8,9],也可以写成a[5:]    fmt.Println(s2)    fmt.Println(s3)}

• Its value is a reference type,
• You can create directly or get a build from the underlying array
• Use Len () to get the number of elements, and the cap () to get the capacity
• In general, use make to create

package mainimport (    "fmt")func main() {    s1 := make([]int, 3, 10) //括号中第一个参数是类型，第二个参数是长度，第三个是容量,如果不设置容量，它就会认为默认是你的长度    fmt.Println(len(s1), cap(s1))}

• If multiple slice point to the same underlying array, one of the value changes affects all
• Make ([]t,len,cap)
• Where the cap can be omitted, then the value of Len is the same
• Len indicates the number of elements present, and the CAP represents the capacity

Slice relationship to the underlying array

package mainimport (    "fmt")func main() {    a := [...]string{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"}    sa := a[2:5]    fmt.Println(sa)    sb := a[3:5]    fmt.Println(sb)}

Reslice

• Reslice indexes are subject to slice slices
• Index can not exceed the capacity cap () value of slice slices
• Index out-of-bounds does not cause redistribution of the underlying array but throws an error

package mainimport (    "fmt")func main() {    a := [...]string{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"}    sa := a[2:5]    fmt.Println(sa)    //这里的sa指向的是一个连续的内存块，所以它的最大容量到这个内存块的底部    fmt.Println(len(sa), cap(sa))    sb := sa[1:3]    fmt.Println(sb)    fmt.Println(len(sb), cap(sb))}//PS结果：PS G:\mygo\src\mytest> go run .\myfirst.go[c d e]3 9[d e]2 8

Append

• You can append elements to the slice tail
• One slice can be appended to the other slice tail
• Returns the original slice if the final length does not exceed the capacity appended to the slice
• If the capacity of the appended slice is exceeded, the array is reassigned and the original data is copied

package mainimport (    "fmt")func main() {    s1 := make([]int, 3, 6)    fmt.Printf("%v, %p \n", s1, s1)    s1 = append(s1, 1, 2, 3)    fmt.Printf("%v, %p \n", s1, s1)    //可以看到两次打印的内存地址是一样的，因为追加的元素没有超出原slice的容量}PS G:\mygo\src\mytest> go run .\myfirst.go[0 0 0], 0xc04203ff50[0 0 0 1 2 3], 0xc04203ff50

package mainimport (    "fmt")func main() {    s1 := make([]int, 3, 6)    fmt.Printf("%v, %p \n", s1, s1)    s1 = append(s1, 1, 2, 3)    fmt.Printf("%v, %p \n", s1, s1)    //可以看到两次打印的内存地址是一样的，因为追加的元素没有超出原slice的容量    s1 = append(s1, 4, 5, 6)    fmt.Printf("%v %p \n", s1, s1)    //此时可以看出，最后一次的打印会重新分配内存地址}PS G:\mygo\src\mytest> go run .\myfirst.go[0 0 0], 0xc04203ff50[0 0 0 1 2 3], 0xc04203ff50[0 0 0 1 2 3 4 5 6] 0xc04203a0c0

package mainimport (    "fmt")func main() {    a := []int{1, 2, 3, 4, 5}    s1 := a[2:5]    s2 := a[1:3]    fmt.Println(s1, s2)    s1[0] = 9    fmt.Println(s1, s2) //slice是指向一个底层的数组，当多个slice指向同一个底层的数组的时候，其中一个发生改变，另外的slice都会发生改变}PS G:\mygo\src\mytest> go run .\myfirst.go[3 4 5] [2 3][9 4 5] [2 9]

package mainimport (    "fmt")func main() {    a := []int{1, 2, 3, 4, 5}    s1 := a[2:5]    s2 := a[1:3]    fmt.Println(s1, s2)    s2 = append(s2, 3, 4, 5, 6, 7, 8, 9, 10) //当append的容量超过底层数组的长度时，会重新分配内存地址并拷贝原始数据    s1[0] = 9    fmt.Println(s1, s2) //slice是指向一个底层的数组，当多个slice指向同一个底层的数组的时候，其中一个发生改变，另外的slice都会发生改变}PS G:\mygo\src\mytest> go run .\myfirst.go[3 4 5] [2 3][9 4 5] [2 3 3 4 5 6 7 8 9 10]

Copy

package mainimport "fmt"func main() {    s1 := []int{1, 2, 3, 4, 5, 6}    s2 := []int{7, 8, 9}    copy(s1, s2) //将S2赋值到s1当中    fmt.Println(s1, s2)}PS G:\mygo\src\mytest> go run .\mysecond.go[7 8 9 4 5 6] [7 8 9]

  Package Mainimport "FMT" Func Main () {s1: = []int{1, 2, 3, 4, 5, 6} s2: = []int{7, 8, 9} s3: = s1[:]/ /complete copy of S1 to S3 FMT. Println (S1, S2) fmt. Println (S3) Fmt. Printf ("%p---%p \ n", S1, S3)}ps g:\mygo\src\mytest> go run. \mysecond.go[1 2 3 4 5 6] [7 8 9][1 2 3 4 5 6]0xc04203ff50- --0XC04203FF50