Add Two Numbers Without The "+" Sign (Bit Shifting Basics)
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Question: Add two integer values without using the "+" operator.
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Table of Contents
The Problem Introduction 0:00 - 0:51
A Way To Think About Number Bases 0:51 - 3:56
Back To The Problem At Hand 3:56 - 4:16
Let's Add Some Numbers (Decimal, Base 10) 4:16 - 4:59
Let's Add Some Numbers (Binary, Base 2) 4:59 - 7:40
Bit Shifting Operators: The 'AND' -> '&' 7:40 - 9:41
Bit Shifting Operators: The 'XOR' -> '^' 9:41 - 11:36
Bit Shifting Operators: The 'Left Shift' -> '
What do you mean? It also works on negative numbers (great explanation of the whole process btw :) ). I used this algorithm on leetcode in C++ (and it has to work with negative numbers as well). The only catch is that I had to convert the carry to unsigned when doing the left bitshift (which wraps the bits around with 1111....11 (32 bits))
int getSum(int a, int b) {
while(b)
{
int carry = a & b; // get all carry bits (all 1&1s)
a = a^b; // sum of disjoint bits (everything except what needs to be carried)
// shift carry by one, as this is how a regular sum operation works
// the carry is moved to the next position
b = (unsigned)carry
yeah
Hey !! This explanation is excellent! But I can't see the code for this problem in the description! Is it moved?
Arun Prakash same here
Thank you for these videos. However, I dont see the code in the description in any of your videos. Am I missing something?
dude, you need to come back and teach us.
the world needs more people like you, blackpenredpen, the organic chemistry teacher, 3blue1brown, nick white, tech with tim, jenny it and many more.
is he working at FAANG now?
@@albertjtyeh53 Back To Back SWE is at twitter!
Corey Schafer and Sentdex are great too
your explanation really helps people who were totally lost, like me.
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Hey man I just wanted to say I think these videos are immensely helpful. The way you explain your thought process on these complex but tiny subjects rashly helps a person change the way they think about code, not to mention learning the lingo of a SWE.
Also please don't ever lose the awkward endings and outtakes.
u r a good teacher bro!
Actually i came here because of your comment in leetcode lol :)
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@@BackToBackSWE I do agree you should make comments on all leet code questions you've solved! That's how I landed on B2B SWE!
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Whenever I get stuck on a problem and see if your video is there, I'm relieved! Thank you man!
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I took compsci and learned this but could never explain to my friend who couldn’t grasp it. She struggled the whole time.
This is such a great explanation and you are an excellent teacher.
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This is the ultimate guide to this hell of bits manipulation. Thank you so much.
Explanation is so good that we won't need to write code for this in interview - just a dry-run with example would do.
ye
Genuinely explained. Excellent, keep doing your work. You`re a great teacher.
thanks.
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This is the best explanation I've ever seen! Thanks a lot!!!
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Dude keep it up, i've learned more from you then my attempt at graduate school lol
ha nice
Likewise!
I have spent literal years glossing over bitshifting because no explanation could come close to me understanding it. I now have at least a basic knowledge and a starting place. Thank you!
Your explanations are always so clear and engaging.
Loved the way you explained even the basics. Thank you.
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This was super helpful !! You're amazing at teaching !
thanks - glad it helped
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Wow. You made it so simple. Thank you sir.
Oh wow! Cool, this was a nice refresher. Great video
Faced this problem in an interview with Qualcomm ... I wish I could see this video earlier to come up with bit manipulation solution :( Thanks a lot for clear explaination!
nice
This is a stupid interview question to ask.. honestly, they don't deserve you.
@@prithazz maybe they wanted to check low level understanding
Thank you for the explanation!!
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Explanation is awesome bro
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So clearly explained, i can't thank enough. 👍
Nicely explained!
You are extremely talented at teaching this stuff, I have struggled with bitwise operations for a while now, however after watching your explanation I was able to implement this myself, which is a major break through.
Thank you for this video!
Glad to know we could help!
Great video. Speaking the entire process through like the computer solidified it for me.
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My Brother, since college back in 1999, I haven't had to use it. But, you have refreshed my way of thinking. Thanks and continue to progress forward!!!!
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nice! good luck
this is so helpful thank you!
this is so helpful. Thank you
thanks for the explanation!
Love you man. I'm in Graduate school & your videos have helped me so much.
That's a pretty intuitive explanation here!
Ive learnt alot today. Ive been struggling these days and i was almost burn out because of the amount of unfinished projects i had. Thank you
Happy to help
Great video man
I am always impressed with your videos. How do you choose the questions? It seems like you have a set of question that you plan to cover and I can feel that those questions are more relevant to actual skills that we need for interviews (not like brain teasers). Also, what's your plan after to cover all planned questions?
I built a list of like 300 when I started this channel. But at some point I just started doing the most burning questions that I felt that I just HAD to try to cover.
And as for plans after I have many questions covered...eh, I don't know. Here is my rough plan for this project: backtobackswe.com/plans
I don't think any human can ever cover all questions. But they can cover all topics and concepts.
This channel is far from the latter.
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very well explained solution!
i think it’s worth noting that this only really works with positive integers
Yeah, true, I'll add that to the notes.
You are amazing! Thank you
Best explanation I've seen. It helped me implement my C# program!
Could you do a similar video for substraction without using arithmetic operators?
This video helped a lot, thanks
You my friend are amazing !! Thanks
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thank you.
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Awesome explanation.. By the way once again thank you for ...
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Best explanation, so thank you, man!
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Thanks for explaining this so clearly
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You are my go to when comes to all questions!
ye
A short video like this about Two's complement would be great.
ok
This was a real cool and intuitive explanation! Thanks!
Thank You, Glad you liked it.
Do check out backtobackswe.com/platform/content
and please recommend us to your family and friends :)
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Man, that's been interesting and fun to listen to you! Thanks! I got topic)
nice
You helped a lot , thank you for making such kind of videos.....
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you really helped with just simple concepts
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Amazing explanation !! Thanks for your effort
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Very good explanation..
Thanks man!
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thanks
Awesome explanation covering from basics 🔥
thx
It was great. Thanks
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Totally understood from zero background. Thumbs up!
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Haven't seen a better explanation. Kudos.
thanks
I start so well, then I just get lost. I have to find a way to get this concepts in my head permanently.
wow. teaching in so simple way. Amazing!
Thank you, glad you liked it 😀
Do check out backtobackswe.com/platform/content
and please recommend us to your family and friends 😀
brilliant explanation~!
Thanks for your vids. I found some inconsistencies with your explanation. At 11:48 you say that when we do shift, '1 gets shifted out'. However, it doesn't.
As an example, take 0101 (5) and 1101(13)
When shifting, we add 0 on the right side and if carry started with 1, it will grow as well. We can't loose the first 1 because just like other 1s in the carry, it specify an index where we need to carry over.
In the provided github code, line 134, it says "1 got shifted out". Again, if we shift it, we will loose part of our answer.
The reason why, at some point, 'carry' becomes 0 and we brake out of the loop, because on 3rd iteration after increasing the carry by one more digit, we will be performing '&' operation between 4 digit (0010) and 5 digit (10000). The result of it will be 00000.
Result of the '^' operation will be 10010 (which, again, won't be possible if we lost that left most '1'.
'carry
Woah, a lot to parse, will need to jog my memory on this one. And nice, hey, I'm in Maryland rn so oof
Great explanation
Thank you! Helped me alot
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Thank you so much, this solve my wondering for years as not an engineer
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Thanks sure - parents....
best explanation, subbed
thanks
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Using that ad to cover the redundant statement was brilliant lmao. I would've never noticed it was repeated if you didn't point it out honestly.
thanks man, it really helped
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Excellent video.
thx
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I just started to study this stuff and my mind is like seeing the light
Awesome explanation!
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Awesome! Thank you very much!!
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