Editorial for DMOPC '17 Contest 5 P2 - Mimi and Binary - Olympiads Online Judge

Editorial for DMOPC '17 Contest 5 P2 - Mimi and Binary

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Author: Kirito

For the first subtask, it suffices to iterate through the suffix $[x_i, \dots]$ ~[x_i, \dots]~ and return the first index where there are $y_i$ ~y_i~ occurrences of $z_i$ ~z_i~.

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

For the second subtask, we can preprocess the array by keeping 2 dynamic arrays, one for zeroes and one for ones, as a second array which holds the index of the $i^\text{th}$ ~i^\text{th}~ index in each of these dynamic arrays. A query can thus be answered in $\mathcal O(1)$ ~\mathcal O(1)~ time by retrieving the index of the left endpoint from the array, and adding $y_i$ ~y_i~, and then finding this index in the dynamic array.

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

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