Do you want to learn python from me with a lot of interactive quizzes, and exercises? Here is my project-based python learning course: codebasics.io/courses/python-for-beginner-and-intermediate-learners

This series gotta be super hit in future

Absolutely hilarious bit at the end. I couldn't stop laughing! 😂 : "If you look at the solution without first solving the problem, it's going to download the covid-19 virus to your computer".

This is literally the best explanation of a stack I have ever seen. I'm someone who dreads data structures and algorithms but after watching this video, I'm actually excited to watch the rest of your DS tutorials. Thank you!

The way, you explain things, I love it. Most loving part is the exercises.

You make some of the easiest to understand explanations for coding stuff that I have come across on the internet. Thank you so much!

"Watch other data structures videos" I will for sure. At first I had curiosity. But now, this channel have my attention.

Data Structures became very interesting with your videos Thank You, sir!!

Simplified way of explanation, I've been trying to find some resources for python dsa and this is the best. !!

Read stacks & queues in 12th class,... but always wondered what its for... browser example really makes sense

Thank you very much, for sharing knowledge for free!

Thanks a lot, It helped me to understand the concept in python. Keep making such good contents. Here is the code of the exercise questions. solution 1: from collections import deque class stack: def __init__(self): self.container=deque() def push(self,val): self.container.append(val) def pop(self): return self.container.pop() def peek(self): return self.container[-1] def is_empty(self): return len(self.container)==0 def size(self): return len(self.container) def reversestring(s): st=stack() for i in s: st.push(i) revstr="" while(st.size()!=0): revstr+=st.pop() return revstr print("this function is for reversing a string using stack") print(reversestring("hello my name is rajnish")) solution 2: from collections import deque class stack: def __init__(self): self.container=deque() def push(self,val): self.container.append(val) def pop(self): return self.container.pop() def peek(self): return self.container[-1] def is_empty(self): return len(self.container)==0 def size(self): return len(self.container) def isbalanced(s): st=stack() flag=0 ch=0 for i in s: if i=="(" or i=="{" or i=="[": ch+=1 st.push(i) if (i==")" and ch==0) or (i=="}" and ch==0) or (i=="]" and ch==0): flag=1 break if i==")" or i=="}" or i=="]": x=st.pop() ch-=1 if x=="(" and i!=")": flag=1 break if x=="{" and i!="}": flag=1 break if x=="[" and i!="]": flag=1 break if flag==1: return "False" else: return "True" print(isbalanced("({a+b})")) print(isbalanced("))((a+b}{")) print(isbalanced("((a+b))")) print(isbalanced("))")) print(isbalanced("[a+b]*(x+2y)*{gg+kk}"))

Your videos are amazing, you make learning Python much easier! Thankyou :)

Second exercise item in this tutorial is a brilliant use of push & pops in stack....! Got the logic for similar set of questions in leetcode. Thank You.

Thank you. You have a great way of explaining concepts . Codebasics for dummies :)

The last one was hilarious..!! 🤣

Covid virus cringe apart, this is a clean and concise video. Thanks!

thank you dear Sir! Your videos are easy to follow and they are very informative. Take care during outbreak

covid-19 on the PC good one :)

sir please make full tutorial on data structures along with algorithm using python with every detail please we newbie programmer need this . and a thanku to you sir for this video

There's so much in my head i need to remember and idk what any of it is for sometimes.

Covid 19 virus 😂, i felt like classroom immediately

Thank you. This playlist have been very helpful. Keep up the great work!

For interview and for oral, this is helpful. Thanks for the videos/

Awesome content! It's great that you're able to squeeze in so much valuable information into a 13 minute video. Also, sorry if I sound pedantic here... but I believe the correct pronunciation of deque is "deck" (written in the documentation at 7:59). Thank you for the valuable content :D

Also, if you inherited deque you wouldn't have to redefine some methods, such as pop, you could just reference the base class method. (I get that this tutorial wasn't about OOP)

simple and precise Thank you!

Super exercises 👍

Thank you. This video help me to understand the subjet.

just a random vdo i clicked nd this is what i got the diamond ,while i was looking for gold.....!!! you're the best sir.

some one told me coding people don't have humour and boring , then i showed them ur channel

so detailed, i like the exercises

It really helps me, Thank you so much!

Why is it that id(list) doesn't change even after append as list is basically a dynamic array?

***solution spoiler***: the use of dictionary in problem 2 was so smart!

thankyou very much sir :)

Diagram for Stack Implementation quick correction 4:52 - Python Code Sample stk = deque() stk.append(5) stk.append(89) # correction 89 not 9 stk.pop() # returns 89

Hi Dhaval, I tried implemening the STACK using Linked list cause I was curious how the dequeue was working behind the scene so here is my solution for the 1st Exercise. Do have a look and if you have any suggestions then let me know.. # Stack using Linked List class Node: def __init__(self, prev = None, data = None, next = None) -> None: self.prev = prev self.data = data self.next = next class Stack: def __init__(self) -> None: self.head = None self.top = None def push(self, data): if self.head == None: node = Node(None, data, None) self.head = node return itr = self.head while itr.next: itr = itr.next node = Node(itr, data, None) itr.next = node self.top = node def pop(self): # print(self.top.data) if self.head == None: return print("Stack is Empty") data = '' if self.top.prev is not None: data = self.top.data self.top.prev.next = None self.top = self.top.prev else: data = self.top.data self.head = None self.top = None return data def peek(self): if self.head == None: return print("Stack is Empty") return self.top.data def print(self): if self.head == None: return print("Stack is Empty") itr = self.head llstr = '' while itr: llstr += f"{ itr.data } => " itr = itr.next print(llstr) def size(self): count = 0 itr = self.head while itr: count += 1 itr = itr.next return count def reverse_string(string): s = Stack() for c in string: s.push(c) rstring = '' while s.size(): rstring += s.pop() print(rstring) s.print() reverse_string("We will conquere COVID-19")

god lvl teaching,,pls expand the series more

thank you so much

Thank you for another extremely useful video! I would like to present my approach on the second exercise. Please reach out and provide feedback for this implementation: from collections import deque class Stack: def __init__(self): self.container = deque() def push(self, val): self.container.append(val) def pop(self): return self.container.pop() def peek(self): return self.container[-1] def is_empty(self): return len(self.container)==0 def size(self): return len(self.container) def reverse_string(a_string): s = Stack() for x in a_string: s.push(x) new_string = '' for y in range(s.size()): new_string += s.pop() return new_string def is_balanced(a_string): s = Stack() d = Stack() check = Stack() for char in a_string: if char in "{}[]()": s.push(char) for char in range(len(s.container)-1, -1, -1): d.push(s.container[char]) #print(s.container) #print(d.container) if len(s.container) != 0 and len(s.container) % 2 == 0: mean = int(len(s.container)/2) for i in range(mean): check.push(s.container[i]+d.container[i]) for set in check.container: if set not in ["[]","()","{}"]: c = False else: c = True return c print(is_balanced("({a+b})")) print(is_balanced("))((a+b}{")) print(is_balanced("((a+b))")) print(is_balanced("))")) print(is_balanced("[a+b]*(x+2y)*{gg+kk}"))

great content ! how is memory management for deque? is it better than list

i am so much grateful to you thank you very much for such clear and neat explanation

Hello Sir, can you please create a video developing of project using only DSA ?

thanks for the support you are adding to the community 🙏

Your theoretical explanation is top notch, but explanation of code sure needs some improvement beginner with the less knowledge have difficulty in understanding

"Download COVID-19 virus". That was really funny 😂. But tutorial was awesome. 🤩🤩

Should this be episode #6?

Wow. Just Amazing Content. Learning.so much through you 🙂

Nice tutorial and it helped me a lot. Waiting for the next set of Data structure tutorials.

can we search for max or min value in stack and make it O(1)?

very helpful

Thanks for this Video it's awesome! Please can you tell me how to puch another value for every node in stack without to adjust the Class Node..?

ThankYou

Instructions weren't clear, now i'm in quarantine

For the example of webbrowser back and forward button, why can't we use doubly linkedlist ?

But how we can overcome the challenge of memory using deque rather than list ?

If one is not able to solve the second exercise on his/her own this means his/her logical skills are weak? I heard a youtuber saying that if you know the basic operations of stacks then you should be able to do it.

why you use self.container? I am learning, I will think just self is enough, I don't know the reason self.container, thanks for help!

Create a video on how to crack the coding interview

Hey in the last exercise why did we returned stack.size()==0 can you explain

sir please create a playlist about python algorithm

4:58 in python code sample typo correction stk.append(89) instead of stk.append(9)

Pandemic is over. So is it ok to click the solution link before I solve? hahahah Thanks for these videos!!

Hey great content. Very very helpful.♥️

in interviews we can use deque? Might be dumb question but im just now learning DS ALGO?

example of website is very useful

I implemented below short solution to the first exercise : from collections import deque def reverse_string(string): lst = [] stack = deque(string) for i in string: lst.append(stack.pop()) return ''.join(lst) print(reverse_string("We will conquere COVID-19")) >>> 91-DIVOC ereuqnoc lliw eW

I am not getting that if we are not giving the length of the List so how it can be get filled??

hye , can we implement stack in python without using in-build function like append and pop ??

Man I have been scratching my heads how to do the second Excersise for 1 day then I had finally to open solution 2 and now m like wait I could have done that.... But seriously damn nice way of implementing hash table to stack earlier I was first trying to see if I can do this with list and ord (of those brackets) to compare them and came up with complicated program but at the end it doesn't work on all test cases I found this to be much better but the last part of the code is really difficult to understand

I think its better my friend if you make the container self._container instead of self.container , private property

i tried the exercise and run your solution. On the last example if I run this print(is_balanced("[a+b]*(x+2y)*{gg+kk}")) the answer is true. But on the debug mode the answer is false. not sure why though.

can we do 2nd ques with the help of regular expressions? if yes then please tell me

i implemented same concept in leetcode problem. it's working but it failed for 9 testcases like '((' , '(['. then i modified it. In Exercise problem: class Solution: def mapper(self, c1, c2): operation = { '}': '{', ')': '(', ']': '[' } return operation[c1] == c2 def isValid(self, s: str) -> bool: stack = Stack() if len(s) == 1: return False for char in s: if char == '(' or char == '{' or char == '[': stack.push(char) if char == ')' or char == '}' or char == ']': if stack.is_empty(): return False if not self.mapper(char, stack.pop()): return False if stack.size() != 0: return False return True

in python: when you add new elements to a list its id address will not change! and I know that python list has no max size. so, if that true, is that mean it's no problem using it as a stack?

The answer is from collections import deque class Stack: def __init__(self): self.container = deque() def push(self, val): self.container.append(val) def pop(self): return self.container.pop() def peek(self): return self.container[-1] def is_empty(self): return len(self.container) == 0 def size(self): return len(self.container) def reverse_string(s): stack = Stack() for ch in s: stack.push(ch) rstr = '' while stack.size()!=0: rstr += stack.pop() return rstr if __name__ == '__main__': print(reverse_string("We will conquere COVI-19")) print(reverse_string("I am the king"))

Solution 1 class stack: def __init__(self): self.stack=deque() self.ans="" def insert(self,ele): self.stack.append(ele) def remove(self): self.stack.pop() def reverse_string(self): ele=self.stack.pop() self.ans+=ele if len(self.stack)!=0: return self.reverse_string() else: return self.ans from collections import deque s1=stack() s1.insert("0") s1.insert("1") s1.insert("2") s1.insert("3") s1.insert("4") print(s1.reverse_string())

I'm watching on my phone and now I'll have to wait till tomorrow to click that link when I'm get my PC 😅 you never know right

class Check: def __init__(self): self.check = deque() def push(self,val): self.check.append(val) def is_paranthesis(self): para = ['{','}','(',')','[',']'] for i in para: return self.check[-1].count(i)==1

Hey man my laptop got virus I think this happend due to checking the solution before doing it 😂😂😜. Anyway Thankyou buddy.

seriously what the heck! i was looking to download covid19 virus but instead downloaded a big fat python.😜

How would you manage this history in terms of data structure if you are browser developer? Not stack but Doubly Linked List. :-P. JFF. I would try stack too.

Why is implementing Stack using a deque a better option than implementing stack using a linked list?

ayooo the repercussions for clicking the solution without doing the exercises has me weak🤣🤣🤣 he litterally said your laptop's going to get corona virus🤣🤣 if you don't do the work first😂

Day 2 : 5:06

12:10 didn't know about the digital variant of this virus

best

Someone said when you were making this video you are the person who was closest to god

can someone please explain this part of code from the solution: if ch==')' or ch=='}' or ch == ']': if stack.size()==0: return False if not is_match(ch,stack.pop()): return False return stack.size()==0

Can anyone explain to me how the memory storage/allocation of stacks work? Do they face similar issues with dynamic arrays (copying and paste each individual data one at a time to the new memory location)? Any help will be much appreciated! Thanks!

what is the difference between append and push?

Here is a different solution for second exercise from collections import deque def parenthesis_matching(equation): stack=deque() arr=deque() for ch in equation: stack.append(ch) for ch in stack: if ch=="(": arr.append("(") elif ch=="[": arr.append("[") elif ch=="{": arr.append("{") elif ch==")": try: arr.remove("(") except: return False elif ch=="]": try: arr.remove("[") except: return False elif ch=="}": try: arr.remove("{") except: return False if len(arr)==0: return True else: return False if __name__=="__main__": s=input("Enter the equation") print(parenthesis_matching(s))

It really download COVID 19... All of the sudden, I'm sick, and so is my computer

@codebasics Sir The creation of class stack is not helping in VScode please help Input: from collections import deque class Stack: def __init__(self): self.container = deque() def push(self, val): self.container.append(val) def pop(self): return self.container.pop() def peek(self): return self.container[-1] def is_empty(self): return len(self.container) == 0 def size(self): return len(self.container) s = Stack() s.push("45") s.push("34") s.peek() s.size() s.pop() s.peek() Output: No output is coming its empty Please Help anyone

I got corona on my pc what do i do now!?!?!?!??! Help!

hi sir,How to print elements of stack

sir please give some easy exercise,the second exercise kills my whole day but i can't find the answer,so i open the sollution,after the open solution i can't understand,most of the comment below in this tutorial is they cant do second exercise sir

CodeWithHarry

Dont try clicking on the solution without trying to solve it first my computer is broken because it installes the COVI-19 virus!