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BEBRAS 2026 Grade 11-12 Round 2 Ext Question 10

BEBRAS · BEBRAS 2026 Grade 11-12 Round 2 Ext

Question 10

Min encodes a row of black/white cells recursively:
- If all cells in the current row are white, write W.
- If all are black, write B.
- Otherwise write X, then encode the left half by the same rules, followed by the right half.

Here are examples.

Question illustration

What is the encoding of this row?

Question illustration

  1. XXXBWBXWXWB
  2. XXXWBXWWXXBBXBW
  3. XXWBWXBXBW
  4. XXXWBWXBXBW