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bogomipz

I’ve spent the last hour browsing and I would like to say this is a great resource for coding problems. I like that the methodology for solving them is discussed for each posting.

Guest

amazing work!

Guest
TartanLlama

This is a pretty impressively large collection of algorithms, but I’m curious how you envisage them being used in an interview setting. I give quite a lot of interviews and I’d never dream of giving most of these as on-the-spot implementation problems.

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Matt Robinson

I watched a google mock interview one time.
The interviewer gave the problem and had the interviewee start working on a solution.
Generally, they would work towards the “obvious” solution (often the first solution shown in the links above). You cant expect everyone to come up with the “best” solution right away. The interviewer then tried to coax the problem solver into finding a better solution with questions such as “what if we can only go over the list once? How can we use the number of occurences to help us? (you get the idea, depends on the problem).”

The optimal solution for many of these are quite clever and very hard to think of. But it gives a good idea of how the interviewee thinks. Also, if you choose a relatively simple problem, if they can at least come up with the “obvious” solution.

Guest

I have been using your website for quite a while and I find it to be absolutely great in DS and Algo preparation for technical interviews. The explanation and the solution TechieDelight provides on most questions is probably the best available online, much better than every other website. Thank you and your team for helping me in my preparation.

Guest

It’s a gift from the CS gods to professors: Here’s several years worth of homework assignments.

Guest

This is really nice, I’m gonna start doing some of them, thanks!

Guest
AlgoLover

A really cool algorithmic problem I’ve been obsessed with lately is stable sorting in O(n log n) time and O(1) extra space. It’s possible (Trabb Pardo 1977, Katajainen and Pasanen, Huang and Langston, etc.) but all known algorithms are very complicated. As far as I understand now, there seems to be a “wall” at sqrt(n) extra space. If we have that much, it’s not too hard to write a stable mergesort or quicksort with the right time complexity. But if we are restricted to O(1) or O(log n) space, the algorithms become much more involved, using a sqrt(n) buffer inside the array to encode information about the rest. There are working implementations on GitHub (GrailSort and WikiSort), both are over 500 lines.

Here’s a couple innocent-looking special cases that are still surprisingly hard:

1) Given an array [a1, a2, …, an, b1, b2, …, bn], rearrange it into [a1, b1, a2, b2, …, an, bn] using O(n) time and O(1) extra space.

2) Given an array of zeroes and ones, sort it stably using O(n) time and O(1) extra space.

I’d be very interested to hear about any advances in this area.

Guest

Very useful work! I would love to see it implemented in many other languages. Any takers? 🙂

Guest

I love STL 🙂

Guest

Well done!!