How would you efficiently remove an element from a slice while preserving order vs without preserving order?

Q: How would you efficiently remove an element from a slice while preserving order vs without preserving order?

// Order-preserving — O(n) due to memory copy func removeOrdered(s []int, i int) []int { return append(s[:i], s[i+1:]...) } // Order-non-preserving — O(1) func removeFast(s []int, i int) []int { s[i] = s[len(s)-1] return s[:len(s)-1] } // Usage s := []int{1, 2, 3, 4, 5} // Remove index 2 (value 3), preserving order result1 := removeOrdered(s, 2) fmt.Println(result1) // [1 2 4 5] s2 := []int{1, 2, 3, 4, 5} // Remove index 2 (value 3), order not preserved result2 := removeFast(s2, 2) fmt.Println(result2) // [1 2 5 4] // Go 1.21+ slices package import "slices" result3 := slices.Delete(s, 2, 3) // order-preserving Use order-preserving for user-visible lists, queues, ordered results Use O(1) swap for internal buffers, worker job queues, sets where order is irrelevant For very frequent removals from large slices, consider a linked list instead Be careful with the shared-array problem: removeOrdered mutates the original backing array Go 1.21 slices package provides slices.Delete() for order-preserving removal

Difficulty: 5/10

slice manipulation, in-place removal, performance tradeoffs

Order-preserving removal is O(n) using append to shift elements. Order-non-preserving removal is O(1) by swapping the target with the last element and truncating.

Two removal strategies

When to choose each approach

1
Use order-preserving for user-visible lists, queues, ordered results
2
Use O(1) swap for internal buffers, worker job queues, sets where order is irrelevant
3

How would you efficiently remove an element from a slice while preserving order vs without preserving order?

Difficulty: 5/10

slice manipulation, in-place removal, performance tradeoffs

Order-preserving removal is O(n) using append to shift elements. Order-non-preserving removal is O(1) by swapping the target with the last element and truncating.

Two removal strategies

When to choose each approach

1
Use order-preserving for user-visible lists, queues, ordered results
2
Use O(1) swap for internal buffers, worker job queues, sets where order is irrelevant
3

How would you efficiently remove an element from a slice while preserving order vs without preserving order?

Order-preserving removal is O(n) using append to shift elements. Order-non-preserving removal is O(1) by swapping the target with the last element and truncating.

How would you efficiently remove an element from a slice while preserving order vs without preserving order?

Order-preserving removal is O(n) using append to shift elements. Order-non-preserving removal is O(1) by swapping the target with the last element and truncating.

Scenario Questions

Follow-up Questions