While a user is downloading a file which is X bytes in size, your job is to provide a function to estimate the time remaining in minutes. The system has a record of the amount (in bytes) B downloaded each minute.
If the file is not completely downloaded, estimate the rate by taking the simple average of the last Z observations.
Write a function:
function solution(X, B, Z);
that returns the amount of time remaining in minutes. X is an integer representing the file size. B is an array of integers listing the bytes downloaded at each minute starting from the beginning of the download until now. Return an integer representing the number of minutes remaining. Z is an integer. You may assume that all the values are reasonable.
Example:
X=100, B=[10,6,6,8], Z=2 30 bytes = 10+6+6+8 have been downloaded. So 70 bytes remain. The average of the last two minutes (Z=2) is 7=(6+8)/2. So the function should return 10 minutes (=70/7).
Note that:
If there are fewer than Z observations, use what you do have.
Your estimate should be rounded up to the nearest integer (ceiling).
If the download is done, return 0
If you are unable to produce an estimate, return -1.
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