AVOID THIS CODING INTERVIEW MISTAKE!

AVOID THIS CODING INTERVIEW MISTAKE!

[GregHogg]

Master data structures and algorithms for FREE at algomap.io :)

[reallyreason]

This is one of like 200 leetcode string-analysis questions where because the inputs are constrained to ASCII characters, you can use a fixed size integer as a bitmapped set indexed by the ASCII character code of each of the jewels. That approach gives time complexity that is linear in N and constant space complexity. If you want to really impress your interviewer on most of these "easy" questions you can learn this intermediate-level technique for creating very efficient implementations of sets.

Another good implementation that is better than this one for is to create a fixed size array and store the count of each letter in `stones` in that array, then simply return the sum of the counts of all the letters in `jewels`. This is worse than the bitset approach on the constant factors in memory consumption and probably also cache performance but has the same asymptotic complexity.

[seventeeenn]

This is way better. But you also use space for the solution

[error-myut]

Hash map laughing in corner after butchering every problem's soul

[pablo-piqz]

it did indeed help lowering my self esteem

[timelimitexceeded]

depends on the maximum length of jewels. if it is not that long, your set algorithm is actually worse. might be slower and requires extra space.

[ericb]

You could argue that the time complexity is O(n) for both, because m will never increase past 52 (if the strings consist of only letters) or at most 255.

[rodrigoqteixeira]

Sets are O(1), but really slow. Use should not use them in small examples, they are only fast on large scale. And in the example of characters a array with 256 length can do it faster than a set (use the unsigned character as an index to the array)

[DavideCanton]

Or you can do Counter(stones) and then sum the counters for each char in jewels

[EverAfterBreak]

That’s really cool observation bro, gotta pay attention to time complexity

[wn]

Although this is slower for small amount data
It is very efficient on large amounts of data

[That_EvilGuy]

But makinv a set, won't that cut out duplicates?

[ZackWhitbord]

This is a great video bro! Thanks for sharing!

[RakshitGoel-yh]

i didn't get how the complexity is n+m instead of N*(numbers of elements in set)

[hamadrehman]

The real gems and jewels are these videos

[theguardianarchives]

Explain the problem first before you jump into solving it

[techniq]

i don't understand why would you use jewels = set([j for j in jewels]) instead of jewels = set(jewels)

[boy_with_thorn]

why not jewels = set(jewels) instead of jewels = set(j for j in jewels)?

[FrozenKnight]

Maybe I'm just not familiar with this language. But why a set instead of a hash table? Or do sets in this language use hash tables?

[iabhisripathi]

Please make a full playlist of leetcode using java