How to remove elements from slice in Golang

Golang is a very popular programming language that is widely used in web development, back-end development, cloud computing and other fields. Slice is one of the very important data structures in Golang. It is similar to an array, but has more powerful features and flexibility. In the process of using slicing, we may encounter situations where we need to delete certain elements. So, how to delete elements in a slice in Golang? This article will introduce it to you in detail.

1. Basic knowledge of Golang slicing

Before formally introducing the slice deletion method, let us first review the basic knowledge of Golang slicing.

1. Definition and declaration of slices

In Golang, we can use the make() function to create a slice.

Sample code:

var s1 []int             //声明一个切片
s2 := []int{1, 2, 3}     //使用字面量创建切片
s3 := make([]int, 5, 10) //使用make()函数创建切片，长度为5，容量为10

2. Features of slices

Unlike arrays, the length of slices can be changed dynamically, which makes it more flexible and practical. Moreover, the underlying layer of slicing is implemented through arrays, so the operations of slicing have many similarities with arrays.

Slices have three important attributes, namely length (len), capacity (cap) and pointer (ptr).

• Length (len): Indicates the number of elements present in the slice.
• Capacity (cap): Indicates the number of elements that can be stored in the underlying array of the slice.
• Pointer (ptr): Points to the address where the first element is stored in the underlying array of the slice.

The following is a sample code showing these properties:

s := make([]int, 3, 5)   //创建一个长度为3，容量为5的切片
s[0], s[1], s[2] = 1, 2, 3

fmt.Println(len(s))      //输出：3
fmt.Println(cap(s))      //输出：5
fmt.Println(&s[0])       //输出：0xc00000a1c0

2. Delete elements in the slice

Next, let’s take a look at how to Delete elements in slice in Golang.

1. Traverse and delete

Traverse the slice and determine whether the elements need to be deleted one by one. If so, use the append() function to reconstruct a new slice. Although this method is feasible, it is not efficient, especially when there are a large number of elements in the slice, the time complexity will be very high.

Sample code:

func RemoveElement(s []int, val int) []int {
    var res []int
    for _, v := range s {
        if v != val {
            res = append(res, v)
        }
    }
    return res
}

2. Use the append() function to delete

We can use the append() function to implement the deletion operation. The specific idea is: First mark the elements to be deleted, and then delete the marked elements after traversing the entire slice.

Sample code:

func RemoveElement(s []int, val int) []int {
    res := make([]int, 0)
    for _, v := range s {
        if v == val {
            continue
        }
        res = append(res, v)
    }
    return res
}

Deleting elements in a slice through this method is actually creating a new slice, so the original slice will not be affected.

3. Internal deletion of slices

In Golang, slices have a powerful feature, which is to support internal deletion. Using the built-in append() function of the slice, you can easily delete the slice.

Sample code:

func RemoveElement(s []int, val int) []int {
    for i := 0; i < len(s); i++ {
        if s[i] == val {
            s = append(s[:i], s[i+1:]...)
            i--
        }
    }
    return s
}

In this example, we use a for loop to iterate through all the elements in the slice. If the element to be deleted is found, the append() function is used to remove the element from the slice. Delete in.

It should be noted that when using the append() function to delete slice elements, you must first delete the elements to be deleted, and then splice the remaining parts back together. In addition, since the slice length will change after deleting elements, we need to decrease the subscript by one after deleting elements to avoid missing some elements.

3. Summary

This article mainly introduces the basic knowledge of slicing in Golang and how to delete elements in the slice. In actual programming, we should combine practical problems and flexibly use multiple methods to achieve a more efficient deletion effect. Hope this article is helpful to you.

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