Editorial for Arcadia Computing Contest 1 P1 - Test Anxiety

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Author: kevlu8

Let the student's current average be denoted as $S_{avg}$ ~S_{avg}~, and the current number of assignments they have completed to be $N$ ~N~. As we know that each assignment is weighted equally and is scored out of 100, we can deduce that the total points they have earned through all assignments so far is $S_{avg}\cdot N$ ~S_{avg}\cdot N~.

The student has one more assignment to complete, thus making the total points possible including the next assignment to be $100(N+1)$ ~100(N+1)~.

In order to attain at least an $80\%$ ~80\%~ average, the student must obtain a total score of at least $80(N+1)$ ~80(N+1)~. If this has already been achieved, simply print $0$ ~0~. Otherwise, print the missing score, which is $80(N+1)-(S_{avg}\cdot N)$ ~80(N+1)-(S_{avg}\cdot N)~. If this missing score is greater than $100$ ~100~, print that it is impossible.

Final complexity: $O(1)$ ~O(1)~

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