How to delete an element from a Slice in Golang

Solution 1:

Order matters

If you want to keep your array ordered, you have to shift all of the elements at the right of the deleting index by one to the left. Hopefully, this can be done easily in Golang:

func remove(slice []int, s int) []int {
    return append(slice[:s], slice[s+1:]...)
}

However, this is inefficient because you may end up with moving all of the elements, which is costy.

Order is not important

If you do not care about ordering, you have the much faster possibility to replace the element to delete with the one at the end of the slice and then return the n-1 first elements:

func remove(s []int, i int) []int {
    s[i] = s[len(s)-1]
    return s[:len(s)-1]
}

With the reslicing method, emptying an array of 1 000 000 elements take 224s, with this one it takes only 0.06ns.

This answer does not perform bounds-checking. It expects a valid index as input. This means that negative values or indices that are greater or equal to the initial len(s) will cause Go to panic.

Slices and arrays being 0-indexed, removing the n-th element of an array implies to provide input n-1. To remove the first element, call remove(s, 0), to remove the second, call remove(s, 1), and so on and so forth.

Solution 2:

Remove one element from the Slice (this is called 're-slicing'):

package main

import (
    "fmt"
)

func RemoveIndex(s []int, index int) []int {
    return append(s[:index], s[index+1:]...)
}

func main() {
    all := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
    fmt.Println(all) //[0 1 2 3 4 5 6 7 8 9]
    all = RemoveIndex(all, 5)
    fmt.Println(all) //[0 1 2 3 4 6 7 8 9]
}