How to delete elements from a slice in go language

Deletion method: 1. Use the "slice object [N:]" statement to delete the first N elements; 2. Use "append(slice object[:i], slice object[i N:].. .)" statement to delete the middle N elements; 3. Use the "slice object [:len(slice object)-N]" statement to delete the last N elements.

The operating environment of this tutorial: Windows 10 system, GO 1.11.2, Dell G3 computer.

Go language deletes elements from slices

Go language does not provide special syntax or interface for deleting slice elements. You need to use the characteristics of the slice itself to delete elements. There are three situations according to the position of the element to be deleted, namely deleting from the beginning, deleting from the middle and deleting from the tail. Among them, deleting elements at the end of the slice is the fastest.

Delete from the beginning

Deleting the beginning element can directly move the data pointer:

a = []int{1, 2, 3}
a = a[1:] // 删除开头1个元素
a = a[N:] // 删除开头N个元素

You can also not move the data pointer, but move the following elements To move the data to the beginning, you can use append to complete it in place (the so-called completion in place means that it is completed in the memory interval corresponding to the original slice data and will not cause changes in the memory space structure):

a = []int{1, 2, 3}
a = append(a[:0], a[1:]...) // 删除开头1个元素
a = append(a[:0], a[N:]...) // 删除开头N个元素

can also be used copy() function to delete the beginning element:

a = []int{1, 2, 3}
a = a[:copy(a, a[1:])] // 删除开头1个元素
a = a[:copy(a, a[N:])] // 删除开头N个元素

Delete from the middle position

To delete the middle element, you need to move the remaining elements as a whole, similarly It can be completed in place with append or copy:

a = []int{1, 2, 3, ...}
a = append(a[:i], a[i+1:]...) // 删除中间1个元素
a = append(a[:i], a[i+N:]...) // 删除中间N个元素
a = a[:i+copy(a[i:], a[i+1:])] // 删除中间1个元素
a = a[:i+copy(a[i:], a[i+N:])] // 删除中间N个元素

Delete from the tail

a = []int{1, 2, 3}
a = a[:len(a)-1] // 删除尾部1个元素
a = a[:len(a)-N] // 删除尾部N个元素

Deleting the elements at the beginning and deleting the elements at the end can be considered as deleting the middle element. For special cases, let’s look at an example.

[Example] Delete the element at the specified position of the slice.

package main
import "fmt"
func main() {
    seq := []string{"a", "b", "c", "d", "e"}
    // 指定删除位置
    index := 2
    // 查看删除位置之前的元素和之后的元素
    fmt.Println(seq[:index], seq[index+1:])
    // 将删除点前后的元素连接起来
    seq = append(seq[:index], seq[index+1:]...)
    fmt.Println(seq)
}

Code output result:

[a b] [d e]
[a b d e]

The code description is as follows:

• Line 1 declares an integer slice and saves the A string from a to e.

• Line 4, for the convenience of demonstration and explanation, use the index variable to save the position of the element that needs to be deleted.

• Line 7, seq[:index] represents the first half of the deleted element, the value is [1 2], seq[index 1:] represents the deleted element The second half of , the value is [4 5].

• Line 10, use the append() function to connect the two slices.

• Line 12 outputs the connected new slice. At this time, the element with index 2 has been deleted.

The essence of deleting slice elements in Go language is to use the deleted element as the dividing point to reconnect the memory of the two parts before and after.

Recommended learning: Golang tutorial

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