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Counting› Clever Counting› 2.1 Bijections and Double Counting
Problem 2.13 ★★★Medium Coming soon

Locks for a Majority Safe

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Section 2.1

Bijections and Double Counting Toolkit
  1. 2.1Counting From the Complements
  2. 2.2Staircase With Hops of Any Size
  3. 2.3Shooting Targets in Columns
  4. 2.4Squares on a Chessboard
  5. 2.5Rectangles on a Chessboard
  6. 2.6Digit Sum From 1 to a Million
  7. 2.7Sum of All Pandigital Numbers
  8. 2.8Sum of Multinomial Coefficients
  9. 2.9Binomial Coefficients With Odd Indices
  10. 2.10Weighted Hockey-Stick Sum
  11. 2.11Magic Triangle Side Sums
  12. 2.12Lines in 3D Tic-Tac-Toe
  13. 2.13Locks for a Majority Safe
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