Editorial for THICC '17 P5 - Smarties - Olympiads Online Judge

Editorial for THICC '17 P5 - Smarties

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Author: Kirito

For $40\%$ ~40\%~ of points, one can iterate through all subarrays, and count how many of them have at least $K$ ~K~ distinct elements.

Time Complexity: $\mathcal O(N^3)$ ~\mathcal O(N^3)~ or $\mathcal O(N^3 \log N)$ ~\mathcal O(N^3 \log N)~

For the remaining $60\%$ ~60\%~ of points, we can employ a two pointer approach. Let there be two pointers, $l$ ~l~ and $r$ ~r~ such that $F[1 \dots r], F[2 \dots r], \dots, F[l \dots r]$ have $K$ ~K~ elements. This can be achieved using a counter array. Implementation is left to the reader as an exercise.

Time Complexity: $\mathcal O(N)$ ~\mathcal O(N)~

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