BASIC CALCULATOR II | LEETCODE 227 | PYTHON SOLUTION

In this video we are solving one of the problems in the Basic Calculator saga: Basic Calculator II. It's arguably the easiest of the Basic Calculator problems and currently a popular Facebook interview question.

It's actually not a hard problem and can be solved in a very efficient manner if you can keep track of the state of the calculation and handle the two edge cases correctly: multiplications and divisions. Stay tuned to find out how!

[yuqian]

Awesome solution! This is much easier to understand and remember than the stack solution. I went with the stack solution before but I always missed some details or forgot certain lines of code every time I reviewed this problem... I hope this solution is acceptable by the interviewer. (I wouldn't be that picky if I am an interviewer but who knows). Thanks again!

[johnangelo]

This made me think how can one ask brain to observe operation without complicating them. This is awesome... I couldn't do it first with this clarity.. Thanks a bunch for clear thought..

[elikiperwasser]

What about multiple multiplications like 2*3*4? The code you wrote will try to undo a summation but there isn't one..

[patb]

For the int(pre / cur) vs pre // curr, I think i would ask the interviewer a clarifying question about how they want integer division to behave first. I'd just go in the direction they suggest me to. If they want to truncate to zero as the leetcode problem does, then i would go with int(pre / cur) as you suggest. I'd adjust appropriately depending on what the interviewer wants.

I got to ask these clarifying questions cause sometimes the interviewers do twists.

Nice solution btw.

[Ankit-hsnb]

5:27 I think a small correction, the previous number is 2 not 3

[TheAdityabhandari]

If you're not using python3, the solution only gets accepted if you convert the res in the division to int(float(prev)/cur)

[vishnuteja]

For division, if you want to truncate to 0, in python3 we would have to use int(float(prev) / curr)

[hooriehmarefat]

Nice solution! Thanks.
As a suggestion, if you can make the code page clearer, that would be awesome because the code page is very blurry and not easy to see.

[zuccca]

This channel is nothing short of pure gold. I am preparing for FAANG interviews currently. Do you offer any kind of 1-on-1 coaching? Please let me know!

[kalyanvejalla]

This solution fails for the test case "14-3/2". Yours returns 12 when the expected is 13. I had to do int(float(prev) / current) for division instead

[ye]

Great solution! Much easier to understand for a beginner ;) just wondering if there is a way to get rid of the i-=1 ? I think I would probably miss it if I got nervous in a real interview.

[wayne]

Really good explanation! Thanks! The idea of undo the previous operation the really good as well as the set prev = prev * cur one.

[symbol]

Took me a while and I had to learn the stack solution first, I suggest everyone learn the stack solution because you can solve all 3 calculator problems with it, but after learning the stack solution I came back here and understood your solution much better. Then I managed to solve Calculator 1 and 3 on my own right after, the stack solution for Calculator 1 worked perfectly for Calculator 3 loll

[yingxu]

always do res -= prev when encountering * and /, what if the previous operation is -

[dnm]

Thank you soo much! You are appreciated!

[bellicosex]

great explanation of the intuition and solution.

[kapilrules]

how did you assumed that curr_operation will always start with +? what if start with other operator?

[naaz]

Why are we setting Prev = cur * prev and not prev = cur?
It will be very helpful if u answer this cause am stuck here

[darleisoares]

Great video, keep those coming, nice job

[kalp]

Explanation at 4:47 is wrong. You want to undo the 3 + 5 operation, so it would be 8 - 5, not 8 - 3. Best to avoid this approach. Stack based approach is much simpler.