Starters_198 Codechef Upsolve Questions Part-3 (Division 4) (Python)

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In competitive programming, "upsolving" means to solve problems after a contest has ended. It's a practice used to improve problem-solving skills by tackling problems that were not solved during the contest.

DISPART (Leave No Witnesses)
Every power-of-2 position (1, 2, 4, 8, ...) is forced to contain 1.
Every position that has no larger supermask within [1, N] is forced to contain 0.
If N itself is a power of 2, the answer is -1 because the highest power of 2 is forced to be both 1 and 0.
For each position, check whether it violates its forced value and count the required flips.
Final answer = total number of positions that need flipping.

Restricted Removals
An element can be deleted only if its current position matches a position in B with the same value.
After every deletion, the array is re-indexed, so elements can move left.
Only the last occurrence of 0 and 1 in B matters (last0 and last1).
Compute the effective position using:
effective_position = current_index - deleted_count
and check whether the element can reach last0 or last1.
Count all deletable elements; answer = N - deletable_elements.

Stable Diffusion (Easy)
Start by assuming every non-empty subarray is stable.
The only bad subarrays are certain long alternating patterns of 1s and 2s.
Treat every gap between adjacent elements as a center and expand outward using two pointers.
Use rem to track the depth of the alternating pattern; when rem ≥ 3, an unstable subarray is found.
Subtract all unstable subarrays from the total number of subarrays to get the final answer.

Do check the official site of python for better understanding.

GitHub : https://github.com/AdityaSrivastava8/Codechef_Upsolve
GitHub : https://github.com/AdityaSrivastava8
Codechef Upsolve (Python) : https://www.youtube.com/playlist?list=PLIXUKrvEGCBB_76GZQr7nAdFVLtaOjYar

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