Hops in a Tetrahedron | Dataford Interview Questions

In a tetrahedron OABC, find the number of ways to start from O and end up at O in exactly N hops

Asked in the Technical 2 stage.

Model the tetrahedron as a graph with vertices O, A, B, and C. Each hop must move along an edge, so staying at the same vertex is not allowed.

Input and Output

Implement count_returning_walks(n), where n is a non-negative integer. Return the exact number of distinct walks that start at O and return to O after exactly n hops.

Constraints

0 <= n <= 10^9
Each hop must follow an edge
Staying at the current vertex is not allowed
Return the exact integer result

Function Signature

def count_returning_walks(n):

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