2 ways to delete an element from a slice

Fast version (changes order)

a := []string{"A", "B", "C", "D", "E"}
i := 2

// Remove the element at index i from a.
a[i] = a[len(a)-1] // Copy last element to index i.
a[len(a)-1] = ""   // Erase last element (write zero value).
a = a[:len(a)-1]   // Truncate slice.

fmt.Println(a) // [A B E D]

The code copies a single element and runs in constant time.

Slow version (maintains order)

a := []string{"A", "B", "C", "D", "E"}
i := 2

// Remove the element at index i from a.
copy(a[i:], a[i+1:]) // Shift a[i+1:] left one index.
a[len(a)-1] = ""     // Erase last element (write zero value).
a = a[:len(a)-1]     // Truncate slice.

fmt.Println(a) // [A B D E]

The code copies len(a) - i - 1 elements and runs in linear time.

Further reading

Slices and arrays in 6 easy steps

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