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Explore Free ProblemsUse these hints if you're stuck. Try solving on your own first.
First, imagine that there is exactly one open door and try to solve the problem.
Now close an opened door.
Then visit k houses by going right. If there is no open door, your assumption of having exactly one open door was right, and you have the answer.
If there is still an open door, go to step 1.
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Problems with circular traversal and state marking patterns are common in top tech interviews. While this exact problem may not always appear, similar logic involving cycle detection, simulation, and constrained operations frequently shows up in FAANG-style interviews.
Most solutions avoid external data structures because the problem is designed with restricted operations. Instead, the state of each house itself acts as a marker during traversal. This allows the algorithm to track progress using constant extra space.
The optimal approach is to traverse the circular street while marking houses using the allowed operations. By changing a house's state when first visited, you can detect when the traversal loops back to the starting point. This helps determine the total number of houses without needing extra memory.
The challenge comes from the circular layout and limited operations available to inspect or modify houses. You must design a strategy that detects cycle completion without traditional tracking structures. Handling state changes carefully while avoiding infinite loops makes the problem tricky.