Burrows-Wheeler Transform

Implement the forward and inverse BWT.

Functions

func BWTForward(data []byte) ([]byte, int)
func BWTInverse(last []byte, primary int) []byte

Behavior

• BWTForward returns the last column and the primary index (row of the original string in the sorted rotations).
• BWTInverse reconstructs the original data from last and primary.
• If data is empty, return []byte{} and primary=0.
• primary is zero-based.

Constraints

• len(data) <= 512 (naive O(n^2 log n) rotation sort is acceptable).

Notes

• Rotations are compared lexicographically as byte sequences.
• The transform is reversible only with the primary index.