Description
1 Programming Assignment
The span si of a stock’s price on a certain day i is the maximum number of consecutive days (up to
and including the current day) that the price of the stock has been less than or equal to its price of
that day i. Given an array P of stock prices such that P[i] is the price of a stock on day i, your job
is to calculate the span for each day. Let’s call it the StockSpan problem. The input and output
of the problem can be described formally as below.
Input: An array P of n non-negative integers, where P[i] is the price of a stock
on day i.
Output: An array S of n positive numbers, where S[i] is the span of the stock
price on day i.
A Java template has been provided containing an empty function CalculateSpan, which takes
an integer array P as its only argument, and returns an integer array. Your task is to write the
body of the CalculateSpan function. You may assume that the input array P will always conform
to the specification above (containing no negative values). Your code is not required to check for
incorrectly formed input data.
You must use the provided Java template as the basis of your submission, and put your implementation inside the CalculateSpan function in the template. You may not change the name,
return type or parameters of the CalculateSpan function. The main function in the template
contains code to help you test your implementation by entering test data or reading it from a
file. You may modify the main function, but only the contents of the CalculateSpan function
will be marked, since the main function will be deleted before marking begins. You can write new
helper functions/methods and can also declare new classes if you need. But you can submit ONLY
the file named “Stock.java”. If you submit multiple files or change the name of the class or the
CalculateSpan function (even lowercase to uppercase or vice versa), your submission may generate
compilation error during the automated testing and you will be graded accordingly.
2 Examples
The table below shows the correct output of the CalculateSpan function on various test inputs.
1
Input Array P Output Array S
1, 5, 6, 8, 7, 9 1, 2, 3, 4, 1, 6
25, 26, 75, 14, 25, 65, 32, 85, 25, 65, 9, 45 1, 2, 3, 1, 2, 3, 1, 8, 1, 2, 1, 2
78, 52, 21, 14, 1, 2, 9, 0 1, 1, 1, 1, 1, 2, 3, 1
3 Evaluation Criteria
The programming assignment will be marked out of 50, based on a combination of automated
testing and human inspection. You may safely assume that the maximum size of an input array
will be 100000.
For an input array containing n values, a brute force solution to the StockSpan problem will
have running time O(n
2
). But the optimal algorithm will have running time O(n). Hint: Use a
stack to achieve the optimal running time.
The mark for each submission will be based on both the asymptotic worst case running time
and the ability of the algorithm to handle inputs of different sizes. The table below shows the
expectations associated with different scores.
Score Description
0 – 10 Submission does not compile or does not conform to the provided
template.
11 – 25 The implemented algorithm is O(n
2
) or is substantially inaccurate
on the tested inputs.
26 – 50 The implemented algorithm is O(n). The numbers would vary
based on how many test cases your algorithm gives correct answer
to.
To be properly tested, every submission must compile correctly as submitted, and must be based
on the provided template. If your submission does not compile for any reason (even trivial mistakes
like typos), or was not based on the template, it will receive at most 10 out of 50. The best way to
make sure your submission is correct is to download it from conneX after submitting and test it.
You are not permitted to revise your submission after the due date, and late submissions will not
be accepted, so you should ensure that you have submitted the correct version of your code before
the due date. conneX will allow you to change your submission before the due date if you notice
a mistake. After submitting your assignment, conneX will automatically send you a confirmation
email. If you do not receive such an email, your submission was not received. If you have problems
with the submission process, send an email to the instructor before the due date.
