Programming Praxis

Today’s exercise is based on a blog entry that Reddit pointed me to. Sean is trying to write a program that finds lines of code in his Python programs that have trailing comments at the ends of lines, which he considers bad style. His naive program improperly flagged a line as containing a trailing comment when the comment marker is embedded in a quoted string:

x = "# This is fine"
"This \# is fine too"
x = "" # This is not

Sean gets a little bit sidetracked in his blog entry, and never quite solves the problem; I’m not convinced the code he writes is correct (though he seems to think it is), and I’m also not convinced that trailing comments are a bad thing. Nevertheless, the task makes an interesting exercise, especially when we also handle quoted escape sequences.

Your task is to write a program that identifies lines of code with trailing comments. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.

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A local maximum of a list of integers is an element of the list at which the adjacent list elements are either less than or equal to the current element; for instance, in the input list (1 2 1 2 3 4 3 2 3 2 1) there are three local maxima, one at the first 2, one at the 4, and one and the last 3. The elements at either end of a list should be considered as greater than the boundary. Only one maximum should be reported for a plateau (consecutive equal maxima).

Your task is to write a program that finds the local maxima of a list of integers. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.

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Alexey Grigorev says:

Most candidates cannot solve this interview problem:

Input: “aaaabbbcca”

Output: [(“a”,4), (“b”,3), (“c”,2), (“a”,1)]

Write a function that converts the input to the output. I ask it in the screening inverview and give it 25 minutes. How would you solve it?

Your task is to write the requested function. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.

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