G-32. Dijkstra's Algorithm - Using Priority Queue - C++ and Java - Part 1 

Let's continue the habit of commenting “understood” if you got the entire video. Please give it a like too, you don't 😞 Do follow me on Instagram: striver_79

Wow, 3 videos on Dijkstra. We will not find such detailed videos even in expensive premium courses.

<a href="#" class="seekto" data-time="926">15:26</a> instead of assigning value using loop , we can just write vector dist ( V , INT_MAX);

Ahh Finally! Here it goes ... Happy to see you back after many days ,was waiting for the new video graph playlist. Thanks a lot for your immense efforts Striver. Good to see you in a new look! Virat Kohli of DSA! 😀

i like how i can write the code myself after being 5 - 6 mins in the video.

Learning Dijkshtra algo for the first time... And understand it in the one watch was like unbelievable.. #striver op

Striver bhaiya cant thank you enough...heard the concept and coded it on one go all credits to you🙏

I have already solved more than 15 problems on Dijextra but i can't resist myself to watch whole video.

thank you for explaining the stuff so well. Every other youtuber I have watched didnt help much but u explain the concept so well and you do the code,

understood, we are so lucky to have u striver

love you man I will watch every second!!! love you for the dedication and series you have contributed for the community

🎯 Key Takeaways for quick navigation: <a href="#" class="seekto" data-time="2">00:02</a> 📚 *Introduction to Dijkstra's Algorithm* - Dijkstra's Algorithm is crucial for solving shortest path problems. - It starts from a source node and finds the shortest distances to all other nodes. <a href="#" class="seekto" data-time="155">02:35</a> 📖 *Implementation Methods* - Dijkstra's Algorithm can be implemented using Priority Queue, Set, or Queue data structures. - Priority Queue and Set are more efficient, with Set being the fastest. <a href="#" class="seekto" data-time="236">03:56</a> 🚀 *Importance of Watching All Videos* - Emphasizes the importance of watching all videos to grasp the concept thoroughly. - Mentions that problem-solving will follow once the concept is clear. <a href="#" class="seekto" data-time="249">04:09</a> 📊 *Representing the Graph* - Explains how to represent a graph using an adjacency list with pairs (node, weight). - Provides an example of storing adjacency information. <a href="#" class="seekto" data-time="364">06:04</a> 🌐 *Initial Configuration* - Describes the initial setup, including the minimum heap data structure and a distance array. - Initializes the source node with a distance of 0. <a href="#" class="seekto" data-time="379">06:19</a> ⏩ *Iteration Process* - Explains the iteration process, similar to BFS, where nodes are processed in order of minimum distance. - Highlights the importance of discovering shorter distances during the iteration. <a href="#" class="seekto" data-time="677">11:17</a> 🧐 *Handling Adjacent Nodes* - Details how to handle adjacent nodes and update their distances. - Demonstrates the process of selecting the best path to each adjacent node. <a href="#" class="seekto" data-time="1083">18:03</a> ❌ *Limitation: Negative Weight Cycles* - Discusses the limitation of Dijkstra's Algorithm when dealing with negative weight edges or cycles. - Explains why negative weights can lead to an infinite loop. <a href="#" class="seekto" data-time="1262">21:02</a> ⏰ *Time Complexity* - Mentions the time complexity of Dijkstra's Algorithm as O(E log V), where E is the number of edges and V is the number of nodes. - Teases upcoming explanations about priority queues and set data structures. Made with HARPA AI

understand Thanks a lot for your immense efforts Striver.

Thank you! I implemented it on my own and it worked without storing the distance on the priority queue. I only stored the nodes themselves. I also used a Pair class to store (dest,weight)

excellent explanation. Lucky to find your channel.❤

Habibi ye bhi kamal video banti ... bahut accha bahut accha

loving this playlist 3000❣

thanku striver .....again i have started this series from where i have stoped due to some reasons ,,,,,i'm sure this time i will complete this

Thank you very much. You are a genius.

bro this is the exact thing i was searching today

Understood! Super fantastic explanation as always, thank you very much!!

U r doing a great job man . Salute to you ..

One suggestion in java code.. Instead of doing 2 operations I.E. peek() and remove() at line number 81,82& 83, we can do one operation pop().. Just an FYI for other java codes... Happy coding.. 👍

half way done ! wont stop

understood,great explanation

Undestood BHAIYA!! thanks alot

<a href="#" class="seekto" data-time="1040">17:20</a> We need to put the node in queue for same distanse too. So we need to put a equality sign over there

Understood Sir, Thank you very much

Great continue this series

Thank you so much ..your videos give me hope that I can do better !!

Awesome Explanation 👍👌

In this implementation it was extremely difficult to figure out the complexity. When we use a visited array, it become clear that a node may be queued multiple times but its neighbors will only be processed once. Because the first occurrence of duplicate node in the queue will have the lightest path and mark the node as visited. Eliminating the need for redundancies to be processed.

This series is far better than any of the netflix original ones

Why the priority queue has been initialized with pair? we can simply take 2-d vector in the pq

You are a Masterpeice!!

Amazing explanation. Thanks Bhaiya

You are hero for us

Amazing explanation

understood, thank you so much.

Love and Respect!

understood very well

Loved it❤

understood brother.❤

great work 👏

Thankyou sir understood🙇‍♂️🙏❤

this stuff is really code . i solved qustn on leetcode based is topic all by myself in 40 min.

Understood Bhaiya😍😍

Superb explanation

IMP: when to apply -> when we have weighted undirected graph , TC -> ElogV as at max our heap has V elements

I guess if you will not check that the if dis != dist[node] we do not have to process this node as it is already processed. Because there can be same nodes with different distance in priority queue. The answer is still corrects, but i guess with your code it might lee to a worst of V.E

what is the need of taking priority queue as in pair , i think there is no need of pair , we can simply take int

nice explaination

understood bhaiya

You are legend !

understood striver!!!

thank you so much 🥰🥰🥰

Thank you bhaiya

can someone explain the priority queue declaration part in java I don't understand the ((x,y) -> x.distance - y.distance ).

understood. Please make playlist on bit masking and bit manipulation

Amazing 👏

@takeUforward Do we need a visited array for Dijikstras algo? On what basis is it be decided if we need a visited array for any type of traversal including BFS/DFS?

striver bhai...dadhi thodi gahri(deep) katt gayi hai side se...😅...this video is greattt.

Good teaching

Thank you sir 😊

Jai Dijkstra's Algorithm 🙇🏼🙏🏻

Understood! :) Thank you for your invaluable efforts striver! _/\_ ^^

amazing🤩🤩

well you are great simple as that

Understood 👌👌

I am so so happy finally i understood this algorithm thankyou ☺

Understood!

can anyone say what is the need for this algorithm because we already found the shortest path in previous lectures of striver??????

Understood 🙏

Understood 👍

hi striver, what is shortest path faster algorithm? SPFA? is it similar to dijkstra?

understood ❤

UNDERSTOOD.

understood!!

understood💙💙💙

Thank You

Understood 😊

pretty good video

thank u bro!

Is there any difference if we use queue at place of priority_queue

Understood❤

Can't thank you enough.

what is the need of taking heap ,cant we just go to neighbour node everytime using adjancency list and check for the distance condition whether it is greater or lower it would then automatically cover all the nodes?

can you tell me whats the diffrence between this and video 29 is it the same?

Is bellman ford applicable to negative weight graph?

This Dijkstra's algorithm is similar to Shortest Path in Undirected Graph with Unit Weights(previous video), only difference is that we don't keep track of the distance in the queue, rather we take it from distance array.I wonder if this makes a difference in the algorithm

Understood !!

Can someone explain ..initialization of priority queue ...first line in the code...why use greater...??

understood

understood😃

Understood.

Understood 😊😇

<a href="#" class="seekto" data-time="711">11:51</a> 10,5 will also be in min-heap of d,n

understood sir :)

Understoood

Understood!!!