How to Move an Item Within a Slice in Go Without Duplication?

Moving an Item Within a Slice in Go

In Go, it is common to manipulate slices, which are dynamic data structures that hold a sequence of elements. One task that you may encounter is moving an item from one position to another within the slice.

To address this, you may attempt the following approach:

slice := []int{0,1,2,3,4,5,6,7,8,9}

indexToRemove := 1
indexWhereToInsert := 4

slice = append(slice[:indexToRemove], slice[indexToRemove+1:]...)
fmt.Println("slice:", slice)

newSlice := append(slice[:indexWhereToInsert], 1)
fmt.Println("newSlice:", newSlice)

slice = append(newSlice, slice[indexWhereToInsert:]...)
fmt.Println("slice:", slice)

However, this approach results in unexpected behavior:

slice: [0 2 3 4 5 6 7 8 9]
newSlice: [0 2 3 4 1]
slice: [0 2 3 4 1 1 6 7 8 9] 

As you noticed, the item in the original position is duplicated when inserted.

Solution:

To correctly move an item within a slice, you can use the following approach:

1. Remove the Item from its Original Position:

   removeItem := slice[indexToRemove]
   updatedSlice := append(slice[:indexToRemove], slice[indexToRemove+1:]...)
   fmt.Println("Updated slice before moving:", updatedSlice)

2. Insert the Item at the New Position:

   insertedSlice := append(updatedSlice[:indexWhereToInsert], removeItem)
   finalSlice := append(insertedSlice, updatedSlice[indexWhereToInsert:]...)
   fmt.Println("Final slice after moving:", finalSlice)

Here's a working code example:

func main() {
    slice := []int{0,1,2,3,4,5,6,7,8,9}

    indexToRemove := 1
    indexWhereToInsert := 4

    removeItem := slice[indexToRemove]
    updatedSlice := append(slice[:indexToRemove], slice[indexToRemove+1:]...)
    fmt.Println("Updated slice before moving:", updatedSlice)

    insertedSlice := append(updatedSlice[:indexWhereToInsert], removeItem)
    finalSlice := append(insertedSlice, updatedSlice[indexWhereToInsert:]...)
    fmt.Println("Final slice after moving:", finalSlice)
}

Output:

Updated slice before moving: [0 2 3 4 5 6 7 8 9]
Final slice after moving: [0 2 3 4 1 5 6 7 8 9]

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