Update READMEs.

Author: trekhleb

src/data-structures/disjoint-set/README.md

@@ -17,4 +17,4 @@ After some operations of *Union*, some sets are grouped together.
 ## References
 
 - [Wikipedia](https://en.wikipedia.org/wiki/Disjoint-set_data_structure)
-- [By Abdul Bari on YouTube](https://www.youtube.com/watch?v=wU6udHRIkcc)
+- [By Abdul Bari on YouTube](https://www.youtube.com/watch?v=wU6udHRIkcc&index=14&t=0s&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)

src/data-structures/hash-table/README.md

@@ -22,4 +22,5 @@ Hash collision resolved by separate chaining.
 
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Hash_table)
+- [Wikipedia](https://en.wikipedia.org/wiki/Hash_table)
+- [YouTube](https://www.youtube.com/watch?v=shs0KM3wKv8&index=4&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)

src/data-structures/heap/README.md

@@ -12,4 +12,5 @@ called the root node.
 
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Heap_(data_structure))
+- [Wikipedia](https://en.wikipedia.org/wiki/Heap_(data_structure))
+- [YouTube](https://www.youtube.com/watch?v=t0Cq6tVNRBA&index=5&t=0s&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)

src/data-structures/linked-list/README.md

@@ -21,4 +21,5 @@ have better cache locality as compared to linked lists.
 
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Linked_list)
+- [Wikipedia](https://en.wikipedia.org/wiki/Linked_list)
+- [YouTube](https://www.youtube.com/watch?v=njTh_OwMljA&index=2&t=1s&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)

src/data-structures/priority-queue/README.md

@@ -14,8 +14,7 @@ with a linked list or an array, a priority queue can be implemented
 with a heap or a variety of other methods such as an unordered 
 array.
 
-
-
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Priority_queue)
+- [Wikipedia](https://en.wikipedia.org/wiki/Priority_queue)
+- [YouTube](https://www.youtube.com/watch?v=wptevk0bshY&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8&index=6)

src/data-structures/queue/README.md

@@ -22,4 +22,5 @@ Representation of a FIFO (first in, first out) queue
 
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Queue_(abstract_data_type))
+- [Wikipedia](https://en.wikipedia.org/wiki/Queue_(abstract_data_type))
+- [YouTube](https://www.youtube.com/watch?v=wjI1WNcIntg&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8&index=3&)

src/data-structures/stack/README.md

@@ -21,4 +21,5 @@ Simple representation of a stack runtime with push and pop operations.
 
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Stack_(abstract_data_type))
+- [Wikipedia](https://en.wikipedia.org/wiki/Stack_(abstract_data_type))
+- [YouTube](https://www.youtube.com/watch?v=wjI1WNcIntg&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8&index=3&)

src/data-structures/tree/README.md

@@ -24,4 +24,5 @@ root node, at the top, has no parent.
 
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Tree_(data_structure))
+- [Wikipedia](https://en.wikipedia.org/wiki/Tree_(data_structure))
+- [YouTube](https://www.youtube.com/watch?v=oSWTXtMglKE&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8&index=8)

src/data-structures/trie/README.md

@@ -19,4 +19,5 @@ prefix tree.
 
 ## References
 
-[Wikipedia](https://en.wikipedia.org/wiki/Trie)
+- [Wikipedia](https://en.wikipedia.org/wiki/Trie)
+- [YouTube](https://www.youtube.com/watch?v=zIjfhVPRZCg&list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8&index=7&t=0s)