Update README URLs based on HTTP redirects

README.md

@@ -166,7 +166,7 @@ It is advised that you write yours first before looking at others'.
 
 | ☆ | Name | Description |
 | --- | --- | --- |
-| ★★★ | [VisuAlgo](http://visualgo.net) | A website featuring a large collection of visualization tools for algorithms and data structures. |
+| ★★★ | [VisuAlgo](https://visualgo.net/) | A website featuring a large collection of visualization tools for algorithms and data structures. |
 | ★★★ | General Practice Helpers: ... [CHelper](https://plugins.jetbrains.com/plugin/7091?pr=idea) (IntelliJ IDEA) ([manual](http://codeforces.com/blog/entry/3273)) ... [caide](https://github.com/slycelote/caide) (Visual Studio, CodeLite) ... [JHelper](http://codeforces.com/blog/entry/13369) (AppCode, CLion) | Great tools that parse contests, inline library codes and provide testing frameworks. They save you from spending your precious time on switching windows and copy-pasting back and forth. |
 | ★★☆ | Codeforces Parsers: ... [Codeforces Parser](https://github.com/johnathan79717/codeforces-parser) ... [GoCF](https://github.com/sukeesh/GoCF) ... [cfparser](https://github.com/gnull/cfparser) (emacs) | These tools parse Codeforces contest problems and help run sample tests. |
 | ★★★ | [The On-Line Encyclopedia of Integer Sequences (OEIS)](https://oeis.org/) | A stunning encyclopedia with a database of countless integer sequences. It also features a powerful search engine. Sometimes a seemingly difficult combinatorics problem could be equivalent to a simple or studied integer sequence. |
@@ -180,7 +180,7 @@ It is advised that you write yours first before looking at others'.
 | --- | --- | --- |
 | ★★★ | [polygon](https://polygon.codeforces.com/) | polygon provides a platform and a rich set of tools for professional contest preparation. ... An example: [Validators with testlib.h - Codeforces](http://codeforces.com/blog/entry/18426) |
 | ★★☆ | [Graph Editor](https://csacademy.com/app/graph_editor/) | A fantasic tool to create and visualize graphs. |
-| ★★☆ | [tcframe](http://tcframe.org) | A C++ framework for generating test cases of competitive programming problems. |
+| ★★☆ | [tcframe](http://tcframe.org/) | A C++ framework for generating test cases of competitive programming problems. |
 | ★★★ | [Virtual Judge (vjudge)](http://vjudge.net) | Virtual Judge (vjudge) allows users to create virtual contests with problems from notable problem archives. |
 | ★★☆ | [BNU Online Judge](https://www.bnuoj.com/v3/) | BNU Online Judge also allows users to create virtual contests. |
 | ★★☆ | [Kattis](https://open.kattis.com/) | Kattis assists in contest preparation (E-mail them for assistance). |
@@ -213,7 +213,7 @@ It is advised that you write yours first before looking at others'.
 
 | ☆ | Name | Description |
 | --- | --- | --- |
-| ★★☆ | [Competitive Programming](http://cpbook.net/), by Steven and Felix Halim | This book contains a collection of relevant data structures, algorithms, and programming tips. It's a well-received book. ... The first edition is free for [download (pdf)](http://www.comp.nus.edu.sg/~stevenha/myteaching/competitive_programming/cp1.pdf). |
+| ★★☆ | [Competitive Programming](https://cpbook.net/), by Steven and Felix Halim | This book contains a collection of relevant data structures, algorithms, and programming tips. It's a well-received book. ... The first edition is free for [download (pdf)](http://www.comp.nus.edu.sg/~stevenha/myteaching/competitive_programming/cp1.pdf). |
 | ★★☆ | [Programming Challenges: The Programming Contest Training Manual](https://www.amazon.com/Programming-Challenges-Contest-Training-Computer/dp/0387001638), by Steven Skiena and Miguel Revilla | This book includes more than 100 programming challenges, as well as the theory and key concepts necessary for approaching them. Problems are organized by topic, and supplemented by complete tutorial material. |
 | ★★★ | [Looking for a Challenge](http://www.lookingforachallengethebook.com/), written by a group of authors associated with the Polish Olympiads | Most of the problems described in the book are really hard but they are explained in such a way that even beginners can understand. It appears to be out of stock (as of Aug, 2016), but you can reserve one on their [official website](http://www.lookingforachallengethebook.com). |
 | ★★☆ | [Computational Geometry: Algorithms and Applications](https://www.amazon.com/Computational-Geometry-Applications-Mark-Berg/dp/3540779736), by Mark de Berg, Otfried Cheong, Marc van Kreveld, Mark Overmars | This is a well-written book which covers a broad range of computational geometry problems. |