LeetCode 1204: Last Person to Fit in the Elevator/Bus [SQL]

[@debashish_dutta]

The first thing that clicked my mind was window function select person_name from (select person_name, SUM(weight) over (order by turn) as running_weight from queue) temp where running_weight

[@samuraychik111]

good query bro !!

[@Rahul-pr1zr]

Nice explanation! I was wondering though - isn't the GROUP BY qualifier needed as part of the SELECT statement or is it optional?

[@ashwinikumar2492]

Interesting solution. I just wanted to know how would this solution fair in comparison to window functions when you have a larger data size and limit?

[@summer_in_california]

AWESOME SOLUTION. thanks for the video!!!

[@YogeshKumar-zb5ms]

how can i do it if the number of people in queue are 100s and it will tka multiple treips, in that case having X

[@frederikmuller]

interesting, I guess you would have to add a condition for the maximum amount of people that the elevator can fit in terms of space.

[@frederikmuller]

for this question you could add WHERE turn

[@sohailkan17]

How's is the self join producing the cummulative sum result I am not getting Can someone explain ?

[@frederikmuller]

it basically just produces every possible join (1 row, 2 rows, 3 rows…) and then sums up the weight. we filter to weights

[@leozeng6696]

The solution in the video fails in PostgreSQL. It doesn't allow me to select the person's name without group by it I need to change it up, so it could work in both MySQL and PostgreSQL SELECT a.person_name FROM queue a JOIN queue b ON a.turn >= b.turn GROUP BY 1 HAVING SUM(b.weight)

[@frederikmuller]

Thank you for providing your solution.

[@عليسعد-ح3ك5ذ]

I have a problem with the condition of the self join , I don't get it

[@frederikmuller]

it basically just produces every possible join (1 row, 2 rows, 3 rows…) and then sums up the weight. we filter to weights

[@عليسعد-ح3ك5ذ]

@@frederikmuller Thank you man ! I tried it on myself and got it , thank you again for replying

[@UmaAndLak]

Thank you for the valuable video Frederick. "Link to the problem" in your comment, does not seem to work.

[@frederikmuller]

The link has actually changed as the question title has changed: leetcode.com/problems/last-person-to-fit-in-the-bus/

[@aznfoever35]

love these man! and great hair

[@frederikmuller]

hehe thanks

[@sandeep6460]

Thanks from India

[@SomeRandomName999999]

Why sum(b.weight) instead of (a.weight)?

[@sonalkulkarni6282]

this is giving wrong answer. I tried to put "weight" in select statement along with person_name just to recheck,, it is fetching wrong value as there are 2 "Thomas Jefferson" names. Please check.

[@samuraychik111]

declare @weight int = 0 declare @turn int = 1 declare @currentweight int while @weight !=1000 begin select @currentweight = (select weight from elevator where turn = @turn) if @currentweight + @weight

[@frederikmuller]

interesting, thanks for sharing 🤔

[@davidreilly5215]

Never thought of joining the tables. I used a window function with cte as ( SELECT person_id, person_name, SUM(weight) OVER(order by turn) as added_weight FROM Queue ) SELECT person_name FROM cte WHERE added_weight

[@frederikmuller]

clever

[@Hsalz]

Not "James Elephant" being 500 lbs. That was intentional.

[@frederikmuller]

I never noticed that 😮

[@shubham900100]

I didnt know kurt hugo schneider was good at SQL

[@riyashussain2473]

why can't we just do HAVING SUM (b.weight)=1000 instead of less than or equal to.

[@ramram99111]

Let's consider currently the sum is 900 Now new person enters whose weight is 110 So the total will be 1110 In these cases we need to consider only till 900.

[@tansmay23]

Finally thank you!

[@vishalbhardwaj969]

You are awesome

[@sandeep6460]

Nice man

[@sandeep6460]

Keep it up

[@dineshshinde1999]

please do not refer his code. its a wrong code

[@frederikmuller]

the question has been updated since recording this video, check out the pinned comment for the updated solution.

[@SagarKumar-db2xy]

Great