Symmetry & invariants
Definition · Level 13 · Interview mechanics
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A trick for puzzles: find a change that leaves the problem the same (swap two ants that bounce, or mirror a process), or a quantity that never changes. The hard part then disappears.
Example
Bouncing ants are the same as ants passing through each other.
Where Tradecraft teaches it
Level 13 · Interview mechanics, in the lesson “Brainteasers: symmetry, speed and working backwards”: Relative speed, symmetry, comparing plans and backward induction: the other half of the classic puzzles.
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