update

README.md

@@ -19,6 +19,7 @@
 - [Tiếng Việt - Vietnamese](translations/README-vi.md)
 - [Español](translations/README-es.md)
 - [Português Brasileiro](translations/README-ptbr.md)
+- [Polish](translations/README-pl.md)
 - [繁體中文](translations/README-tw.md)
 
 </details>
@@ -36,7 +37,6 @@
 - [Ukrainian](https://github.com/jwasham/coding-interview-university/issues/106)
 - [Korean(한국어)](https://github.com/jwasham/coding-interview-university/issues/118)
 - [Telugu](https://github.com/jwasham/coding-interview-university/issues/117)
-- [Polish](https://github.com/jwasham/coding-interview-university/issues/122)
 - [Urdu](https://github.com/jwasham/coding-interview-university/issues/140)
 - [Thai](https://github.com/jwasham/coding-interview-university/issues/156)
 - [Greek](https://github.com/jwasham/coding-interview-university/issues/166)
@@ -242,7 +242,6 @@ Sometimes the classes are not in session so you have to wait a couple of months,
 
 - [ ] [ABC: Always Be Coding](https://medium.com/always-be-coding/abc-always-be-coding-d5f8051afce2#.4heg8zvm4)
 - [ ] [Whiteboarding](https://medium.com/@dpup/whiteboarding-4df873dbba2e#.hf6jn45g1)
-- [ ] [Effective Whiteboarding during Programming Interviews](http://www.coderust.com/blog/2014/04/10/effective-whiteboarding-during-programming-interviews/)
 - [ ] [Demystifying Tech Recruiting](https://www.youtube.com/watch?v=N233T0epWTs)
 - [ ] How to Get a Job at the Big 4:
     - [ ] [How to Get a Job at the Big 4 - Amazon, Facebook, Google & Microsoft (video)](https://www.youtube.com/watch?v=YJZCUhxNCv8)
@@ -496,11 +495,11 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
 - ### Arrays
     - Implement an automatically resizing vector.
     - [ ] Description:
-        - [Arrays (video)](https://www.coursera.org/learn/data-structures/lecture/OsBSF/arrays)
+        - [Arrays (video)](https://www.coursera.org/lecture/data-structures/arrays-OsBSF)
         - [UC Berkeley CS61B - Linear and Multi-Dim Arrays (video)](https://archive.org/details/ucberkeley_webcast_Wp8oiO_CZZE) (Start watching from 15m 32s)
         - [Basic Arrays (video)](https://archive.org/details/0102WhatYouShouldKnow/02_04-basicArrays.mp4)
         - [Multi-dim (video)](https://archive.org/details/0102WhatYouShouldKnow/02_05-multidimensionalArrays.mp4)
-        - [Dynamic Arrays (video)](https://www.coursera.org/learn/data-structures/lecture/EwbnV/dynamic-arrays)
+        - [Dynamic Arrays (video)](https://www.coursera.org/lecture/data-structures/dynamic-arrays-EwbnV)
         - [Jagged Arrays (video)](https://www.youtube.com/watch?v=1jtrQqYpt7g)
         - [Jagged Arrays (video)](https://archive.org/details/0102WhatYouShouldKnow/02_06-jaggedArrays.mp4)
         - [Resizing arrays (video)](https://archive.org/details/0102WhatYouShouldKnow/03_01-resizableArrays.mp4)
@@ -532,14 +531,14 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
 
 - ### Linked Lists
     - [ ] Description:
-        - [ ] [Singly Linked Lists (video)](https://www.coursera.org/learn/data-structures/lecture/kHhgK/singly-linked-lists)
+        - [ ] [Singly Linked Lists (video)](https://www.coursera.org/lecture/data-structures/singly-linked-lists-kHhgK)
         - [ ] [CS 61B - Linked Lists 1 (video)](https://archive.org/details/ucberkeley_webcast_htzJdKoEmO0)
         - [ ] [CS 61B - Linked Lists 2 (video)](https://archive.org/details/ucberkeley_webcast_-c4I3gFYe3w)
     - [ ] [C Code (video)](https://www.youtube.com/watch?v=QN6FPiD0Gzo)
             - not the whole video, just portions about Node struct and memory allocation.
     - [ ] Linked List vs Arrays:
-        - [Core Linked Lists Vs Arrays (video)](https://www.coursera.org/learn/data-structures-optimizing-performance/lecture/rjBs9/core-linked-lists-vs-arrays)
-        - [In The Real World Linked Lists Vs Arrays (video)](https://www.coursera.org/learn/data-structures-optimizing-performance/lecture/QUaUd/in-the-real-world-lists-vs-arrays)
+        - [Core Linked Lists Vs Arrays (video)](https://www.coursera.org/lecture/data-structures-optimizing-performance/core-linked-lists-vs-arrays-rjBs9)
+        - [In The Real World Linked Lists Vs Arrays (video)](https://www.coursera.org/lecture/data-structures-optimizing-performance/in-the-real-world-lists-vs-arrays-QUaUd)
     - [ ] [why you should avoid linked lists (video)](https://www.youtube.com/watch?v=YQs6IC-vgmo)
     - [ ] Gotcha: you need pointer to pointer knowledge:
         (for when you pass a pointer to a function that may change the address where that pointer points)
@@ -561,11 +560,11 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
         - [ ] reverse() - reverses the list
         - [ ] remove_value(value) - removes the first item in the list with this value
     - [ ] Doubly-linked List
-        - [Description (video)](https://www.coursera.org/learn/data-structures/lecture/jpGKD/doubly-linked-lists)
+        - [Description (video)](https://www.coursera.org/lecture/data-structures/doubly-linked-lists-jpGKD)
         - No need to implement
 
 - ### Stack
-    - [ ] [Stacks (video)](https://www.coursera.org/learn/data-structures/lecture/UdKzQ/stacks)
+    - [ ] [Stacks (video)](https://www.coursera.org/lecture/data-structures/stacks-UdKzQ)
     - [ ] [Using Stacks Last-In First-Out (video)](https://archive.org/details/0102WhatYouShouldKnow/05_01-usingStacksForLast-inFirst-out.mp4)
     - [ ] Will not implement. Implementing with array is trivial.
 
@@ -604,12 +603,12 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
         - [ ] [Using Hash Tables (video)](https://archive.org/details/0102WhatYouShouldKnow/06_03-usingHashTables.mp4)
         - [ ] [Supporting Hashing (video)](https://archive.org/details/0102WhatYouShouldKnow/06_04-supportingHashing.mp4)
         - [ ] [Language Support Hash Tables (video)](https://archive.org/details/0102WhatYouShouldKnow/06_05-languageSupportForHashTables.mp4)
-        - [ ] [Core Hash Tables (video)](https://www.coursera.org/learn/data-structures-optimizing-performance/lecture/m7UuP/core-hash-tables)
-        - [ ] [Data Structures (video)](https://www.coursera.org/learn/data-structures/home/week/3)
-        - [ ] [Phone Book Problem (video)](https://www.coursera.org/learn/data-structures/lecture/NYZZP/phone-book-problem)
+        - [ ] [Core Hash Tables (video)](https://www.coursera.org/lecture/data-structures-optimizing-performance/core-hash-tables-m7UuP)
+        - [ ] [Data Structures (video)](https://www.coursera.org/learn/data-structures/home/week/4)
+        - [ ] [Phone Book Problem (video)](https://www.coursera.org/lecture/data-structures/phone-book-problem-NYZZP)
         - [ ] distributed hash tables:
-            - [Instant Uploads And Storage Optimization In Dropbox (video)](https://www.coursera.org/learn/data-structures/lecture/DvaIb/instant-uploads-and-storage-optimization-in-dropbox)
-            - [Distributed Hash Tables (video)](https://www.coursera.org/learn/data-structures/lecture/tvH8H/distributed-hash-tables)
+            - [Instant Uploads And Storage Optimization In Dropbox (video)](https://www.coursera.org/lecture/data-structures/instant-uploads-and-storage-optimization-in-dropbox-DvaIb)
+            - [Distributed Hash Tables (video)](https://www.coursera.org/lecture/data-structures/distributed-hash-tables-tvH8H)
 
     - [ ] implement with array using linear probing
         - hash(k, m) - m is size of hash table
@@ -629,7 +628,7 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
         - binary search using recursion
 
 - ### Bitwise operations
-    - [ ] [Bits cheat sheet](https://github.com/jwasham/coding-interview-university/blob/master/extras/cheat%20sheets/bits-cheat-cheet.pdf) - you should know many of the powers of 2 from (2^1 to 2^16 and 2^32)
+    - [ ] [Bits cheat sheet](https://github.com/jwasham/coding-interview-university/blob/master/extras/cheat%20sheets/bits-cheat-sheet.pdf) - you should know many of the powers of 2 from (2^1 to 2^16 and 2^32)
     - [ ] Get a really good understanding of manipulating bits with: &, |, ^, ~, >>, <<
         - [ ] [words](https://en.wikipedia.org/wiki/Word_(computer_architecture))
         - [ ] Good intro:
@@ -640,6 +639,7 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
         - [ ] [Bithacks](https://graphics.stanford.edu/~seander/bithacks.html)
         - [ ] [The Bit Twiddler](https://bits.stephan-brumme.com/)
         - [ ] [The Bit Twiddler Interactive](https://bits.stephan-brumme.com/interactive.html)
+        - [ ] [Bit Hacks (video)](https://www.youtube.com/watch?v=ZusiKXcz_ac)
     - [ ] 2s and 1s complement
         - [Binary: Plusses & Minuses (Why We Use Two's Complement) (video)](https://www.youtube.com/watch?v=lKTsv6iVxV4)
         - [1s Complement](https://en.wikipedia.org/wiki/Ones%27_complement)
@@ -656,8 +656,8 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
 ## Trees
 
 - ### Trees - Notes & Background
-    - [ ] [Series: Core Trees (video)](https://www.coursera.org/learn/data-structures-optimizing-performance/lecture/ovovP/core-trees)
-    - [ ] [Series: Trees (video)](https://www.coursera.org/learn/data-structures/lecture/95qda/trees)
+    - [ ] [Series: Core Trees (video)](https://www.coursera.org/lecture/data-structures-optimizing-performance/core-trees-ovovP)
+    - [ ] [Series: Trees (video)](https://www.coursera.org/lecture/data-structures/trees-95qda)
     - basic tree construction
     - traversal
     - manipulation algorithms
@@ -731,8 +731,7 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
         - [ ] sift_down - needed for extract_max
         - [ ] remove(i) - removes item at index x
         - [ ] heapify - create a heap from an array of elements, needed for heap_sort
-        - [ ] heap_sort() - take an unsorted array and turn it into a sorted array in-place using a max heap
-            - note: using a min heap instead would save operations, but double the space needed (cannot do in-place).
+        - [ ] heap_sort() - take an unsorted array and turn it into a sorted array in-place using a max heap or min heap
 
 ## Sorting
 
@@ -1085,7 +1084,7 @@ Graphs can be used to represent many problems in computer science, so this secti
 - ### Networking
     - **if you have networking experience or want to be a reliability engineer or operations engineer, expect questions**
     - otherwise, this is just good to know
-    - [ ] [Khan Academy](https://www.khanacademy.org/computing/computer-science/internet-intro)
+    - [ ] [Khan Academy](https://www.khanacademy.org/computing/computer-science/computers-and-internet-code-org)
     - [ ] [UDP and TCP: Comparison of Transport Protocols (video)](https://www.youtube.com/watch?v=Vdc8TCESIg8)
     - [ ] [TCP/IP and the OSI Model Explained! (video)](https://www.youtube.com/watch?v=e5DEVa9eSN0)
     - [ ] [Packet Transmission across the Internet. Networking & TCP/IP tutorial. (video)](https://www.youtube.com/watch?v=nomyRJehhnM)
@@ -1217,7 +1216,7 @@ Graphs can be used to represent many problems in computer science, so this secti
             - rough overview of any key algorithm that drives the service
             - consider bottlenecks and determine solutions
     - Exercises:
-        - [Design a CDN network: old article](http://repository.cmu.edu/cgi/viewcontent.cgi?article=2112&context=compsci)
+        - [Design a CDN network: old article](https://kilthub.cmu.edu/articles/Globally_distributed_content_delivery/6605972)
         - [Design a random unique ID generation system](https://blog.twitter.com/2010/announcing-snowflake)
         - [Design an online multiplayer card game](http://www.indieflashblog.com/how-to-create-an-asynchronous-multiplayer-game.html)
         - [Design a key-value database](http://www.slideshare.net/dvirsky/introduction-to-redis)
@@ -1297,20 +1296,26 @@ Coding Interview Question Videos:
 - [Tushar Roy (5 playlists)](https://www.youtube.com/user/tusharroy2525/playlists?shelf_id=2&view=50&sort=dd)
     - Super for walkthroughs of problem solutions.
 - [Nick White - LeetCode Solutions (187 Videos)](https://www.youtube.com/playlist?list=PLU_sdQYzUj2keVENTP0a5rdykRSgg9Wp-)
-    - These are my new favorite. You can watch several in a short time.
     - Good explanations of solution and the code.
+    - You can watch several in a short time.
+- [FisherCoder - LeetCode Solutions](https://youtube.com/FisherCoder)
 
 Challenge sites:
 - [LeetCode](https://leetcode.com/)
-- [TopCoder](https://www.topcoder.com/)
-- [Project Euler (math-focused)](https://projecteuler.net/index.php?section=problems)
-- [Codewars](http://www.codewars.com)
-- [HackerEarth](https://www.hackerearth.com/)
+    - My favorite coding problem site. It's worth the subscription money for the 1-2 months you'll likely be preparing.
+    - [LeetCode solutions from FisherCoder](https://github.com/fishercoder1534/Leetcode) 
+    - See Nick White Videos above for short code-throughs
 - [HackerRank](https://www.hackerrank.com/)
-- [Codility](https://codility.com/programmers/)
+- [TopCoder](https://www.topcoder.com/)
 - [InterviewCake](https://www.interviewcake.com/)
 - [Geeks for Geeks](http://www.geeksforgeeks.org/)
 - [InterviewBit](https://www.interviewbit.com/invite/icjf)
+- [Project Euler (math-focused)](https://projecteuler.net/index.php?section=problems)
+
+Language-learning sites, with challenges:
+- [Codewars](http://www.codewars.com)
+- [Codility](https://codility.com/programmers/)
+- [HackerEarth](https://www.hackerearth.com/)
 - [Sphere Online Judge (spoj)](http://www.spoj.com/)
 - [Codechef](https://www.codechef.com/)
 
@@ -1321,6 +1326,7 @@ Mock Interviews:
 - [Gainlo.co: Mock interviewers from big companies](http://www.gainlo.co/) - I used this and it helped me relax for the phone screen and on-site interview.
 - [Pramp: Mock interviews from/with peers](https://www.pramp.com/) - peer-to-peer model of practice interviews
 - [Refdash: Mock interviews and expedited interviews](https://refdash.com/) - also help candidates fast track by skipping multiple interviews with tech companies.
+- [interviewing.io: Practice mock interview with senior engineers](https://interviewing.io) - anonymous algorithmic/systems design interviews with senior engineers from FAANG anonymously. 
 
 
 ## Once you're closer to the interview
@@ -1970,4 +1976,4 @@ Sit back and enjoy. "Netflix and skill" :P
 
 ## LICENSE
 
-[CC-BY-SA-4.0](./LICENSE.txt)
+[CC-BY-SA-4.0](./LICENSE.txt)