Dp 25. Longest Common Subsequence | Top Down | Bottom-Up | Space Optimised | DP on Strings
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- Опубликовано: 28 фев 2022
- Lecture Notes/C++/Java Codes: takeuforward.org/dynamic-prog...
Problem Link: bit.ly/3pvkqUd
Pre-req for this Series: • Re 1. Introduction to ...
a
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Full Playlist: • Striver's Dynamic Prog...
In this video, we solve the LCS Dp, this is the first problem on the pattern Strings on DP.
If you have not yet checked our SDE sheet, you should definitely do it: takeuforward.org/interviews/s...
You can also get in touch with me at my social handles: linktr.ee/takeUforward
In the future, Mr. Vikramaditya will go down as the G.O.A.T online DSA teacher.
Yes he is GOAT
I am the future
He is already for me.
Understood and you've completely changed my life. Doesn't matter if I get placed in a good company or not but the quality of this lectures are supreme and I will carry this knowledge for rest of my life.
Keep trying. It will work out. Dream for the day when you are so good that you REJECT your dream company.
@@AdityaKumar-be7hx Requires god level consistency to do that.
You will probably forget the concepts, since these are never used in the industry. What a satire !
🤣🤣@@idris110
brother are you placed
If someone is following Striver's series then this LCS is also a cakewalk..#Striver gives u confidence and you are no longer scared of dp😁
putting your years of hardwork in some videos ,how lucky we are,Thanks a lot striver bhaiya for everything you are doing for us
46:05 for space optimization we don't require the loop for prev as the values are already zero in it.
Loop is required in C++ to initialize array with 0s. But for Java it is not required as by default array is declared with 0s.
Protect this guy at all costs. Thank you sir for all your hard work in making this video.
Everyone should be protected bro
No other video on the topic will offer you a better explanation than this! This is just pure teaching excellence! Subscribed.
I am very grateful to you for uploading this playlist. This is great!!!!!!!!!!!!!!!!!!!!!
Understood.
You're a great teacher. If possible, please do problems about DP on tree. I struggle with them. Thank you!
understood bhaiya!!! after a very long time i am back to your channel....previously i was doing a race that as soon as you upload the video, i should watch it then n there, before the next video gets uploaded in this dp series, but due to some busy schedule, i lost the race. yeah, but your quality and energy is still the same as your starting videos
This was life-changing. Thank you Striver, you taught what paid courses could not for so many years. I wish I had discovered your site earlier; it would have saved so much time and energy.
bro!!!!!! What an explanation, absolutely brilliant. I am starting to love coding now. Thanks
What an easy explanation, loved it !
absolutely minds bogling.i am not kidding i wasn't able to solve simple recusion questions few weeks ago now i can solve medium and hard dp questions on my own without watching videos.all i can say thank you striver.
Its taking while to digest this information for me ,
Just imagine the efforts this guy is adding to make it available for everyone.
You can't find better explanation than this, Brilliant!!
bro striver you have taught so well that i didnt even need to watch the video,i solved the problem in all three ways,thaank you very much❤
understood, always in awe of you genius and hard working you are:)
I used to be scared of Dp when I started coding journey, but when I am actually doing it, it's cake walk. Thankyou striver for sharing your knowledge.
UNDERSTOOD.....Thank You So Much for this wonderful video............🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻
15:34 "You kow i am hearing you" in the background
So?
I’m just so thankful to you for this wonderful series, I’m honestly enjoying it dude, surely you’re one of the best!
I even did the problem by myself so easily, i was shocked believing😂
me too😂
Understood! Awesome explanation as always, thank you very much!!!
understood.wonderful. amazing. hats-off. unmatchable.
Understood,you are doing the great job , very thankful to you
You are amazing ❤️.
Thanks a lot for this valuable content 🙌🙇🙇
Giving my best shot for preparing for my placements. Let's see what happens in upcoming months. Great Content
US ❤
I should mention I am solving DSA consistently from past 1 year. Encountered this question a lot of times.
But till date this is the best explanation boss❤
Very nice explanation sir, Thank you!
Thanks bro the Playlist is top notch...am getting a lot better...Thanks again
Loved the Explanation!!Understood
UNDERSTOOD...
Thanks striver for the video... :)
awesome, understood..was pretty easy due to what you've alrready taught
Thank you so much bhaiya, I always heard of this question as one of the most difficult ones. But by following your DP series, I did it on my own. You can easily sell this quality content for ₹ 50k but you're giving it for free. BEST TEACHER EVER ♥♥♥♥
Understood, Thank you so so much.
I was able to see that curr= prev; mistake as you were typing it. thanks to you Striver. you are the best
Can we do using single array if we denote prev[j-1] in a variable, keep updating it after every iteration of inner loop ?
hey man i know you are a very good teacher , but you are also a very good human being.
Just one word , Beautiful!
Man the content is gold.
seriously you are a legit!
understood ,thanks🙌
Thanks for great explanation striver
what an explanation thanks for your time and such video
simple space optimization technique : just 2,3 chanes
instead of using 2 different vectors we can just change dimension of dp to [no of previous rows we wanred + 1][no of colum]
int longestCommonSubsequence(string s1, string s2) {
vectordp(2, vector(s2.size()+1, 0)); // changing dimension as per need
for(int i=1; i
I solved with different tabulation approach (without shifting index) as below:
int m=text1.length();
int n=text2.length();
int[][] dp = new int[m][n];
int temp=0;
for(int i=0; i
same
Nice explanation raj bhaiyan or dude, I might call you angel!🥰🥰
Very good explanation. Understood. Thanks.
Dhonnobad Brother
You are great
Thank You Very much Striver !
In Tabulation we are declaring vector with values zero. So we can skip first two loops.
Thanks a lot striver
Awesome lecture. Understood!
Why can't we put the base case at index 0? Especially for LCS - DP on strings related questions?
understood,previously I mugged up the tabulation formula for the exam ,but now I know how it came.
very well explained step by step
hey great video but isn't the auxiliary stack space supposed to be max(s.size(), t.size())?
Understood boss man!
Understood!!!
Same tabulation method that you taught in previous videos... Same approach without index shifting.
Base case in Memoization :
if(index1 == 0 || index2 == 0) {
return s1.charAt(index1) == s2.charAt(index2) ? 1 : 0;
}
Tabulation :
static int tabulation(int index1, int index2, String s1, String s2) {
int[][] dp = new int[s1.length()][s2.length()];
dp[0][0] = s1.charAt(0) == s2.charAt(0) ? 1 : 0;
for(int i = 1; i
Understood. Only one point, if you are doing the tabulation to eliminate the O(m*n) S.C and then including (m+n) extra space for an extra row and column, it seems a bit redundant.
m+n
very good explanation
Thank you Striver for such a wonderful explanation. Finally understood it intuitively. 💯💯
Love the concept ✨
Understood, sir. Thank you very much.
Thanks Striver. Understood LCS.
I deeply understand recursion, memoization, tabulation and space optimization.
GOAT for a reason❤❤
awesome paaji
understood bruh, plz make video on sliding window technique too.
striver help this brother out!
how you are staying disicplined?
so far you are single ,right?
how you are avoiding every distractions and focusing on your goal
please make a video on this brother!!
hey striver this is regarding ur tuf website......one feedback....can you add another checklist to mark important or tough nut questions so that for revision we can se it carefully again....because this subsequence is screewing up my brain :)
Great explanation!
Understood Sir!
Explained Like a Dopamine Hit!
Understood sir ! 🙏🙏
Striver, why can't we return INT_MIN , in the base case. Because if we return 0, it will be added to 1 and the resultant number will be considered for maximum. And even if it is not the maximum, it will be returned. Your explanation is very intuitive.
Believe or not Striver
I solved the problem by myself without seeing this video
Note : I gone through all your previous dp videos properly with no skip :)
I am so happy.. Thanks to you.
thank you so much!
Again @takeUforwad, just letting you know, again that's stuff you have done, is GOD's own work, thank you for from bottom of my heart, thanks !!!
If someone is using java to write the code, in space optimization approach there will be error in a testcase, to resolve that error replace prev = curr with prev = curr.clone(); or else use the code snippet
int [] temp = prev;
prev = (curr);
curr = temp;
Because in java prev = curr will not create a new array but it will point both the references to same address.
Your program would work fine.
you are too awesome bro
one of the best dp series
Love you bro :) you are saviour!
This man is saviour. Thanks bhaiya ❤️
Understood❤❤🔥🔥
We don't need to add base case while bottom-up in case of index shifting. If we just replace "-1" with "0" while initializing dp vector. Isn't it?
did it in 1st attempt without seeing the video, shifting index to right was new to me
Decode ways is a new kind of pattern on dp on strings i think and that can be covered
In interviews do we need to show the overlapping subproblems by taking longer examples or we can simply move on with memoization?
take till 5 to 6 steps., if recruiter does want , want he will tell u., to move to next step.
love this!
beautifully explained thanks a lot!!
Understood ❤
UNDERSTOOD!
nice explaination !
understood well !
understood !!
Can anyone please explain why (index1 == 0 || index2 == 0) has not been considered as base case here as we did in DP of arrays?
In DP of Arrays, I was trying to use (index < 0) as the base case, but when I saw Striver's video, I changed my approach to his, where he was considering (index == 0 ) as the base case. But now, in this, he is using the other way around.
Can someone please explain why?
You can use index1 == 0 || index2 == 0 but then it will have 2 cases 1) if(index1 == 0 && index2 == 0) return s1[index1] == s2[index2] ;
2) if(index1 == 0 || index2 == 0) \\ using loop find the single character(having index == 0) in other string if present return 1 else return 0
therefore it is difficult to find and index < 0 base case is much easier so it's better to write that
Understood!
You are a legend!
Excellent explanation bro
best dp playlist on youtube