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Comment by option_greek | Hacker News Reader

Wait till this appears on LeetCode and gets included in the FAANG whiteboard interviews to be solved in 15 minutes.

I know you’re joking, but apparently it was given as a programming problem in a contest on at least one occasion.

Here’s another more recent case where it appeared in a coding contest: https://discuss.codechef.com/questions/133115/wrong-problem-...

It has been asked in real interviews

That’s a different (rather easier) problem: note that the safe combination can contain the same digit more than once.

The solution to this problem is given by de Bruijn sequences: https://en.wikipedia.org/wiki/De_Bruijn_sequence

Ah, I see. Thanks

Yeah, I was thinking the same thing. Seems very similar to this problem: https://leetcode.com/problems/cracking-the-safe/

And can confirm that at least one FAANG company has asked this in a real interview.

Haven't taken the time to read through this properly so forgive the question - but is this any different from the above problem?

And if so - if someone solves this programming task on leetcode have they not then also solved the permutation problem from OP?

It is different because a safe combination may contain the same digit more than once, so the intended solution is a de Bruijn sequence: https://en.wikipedia.org/wiki/De_Bruijn_sequence