Add page for past practice contests

Author: aiviaghost

_data/pages.yml

@@ -17,3 +17,7 @@
 - name: Events
   url: /events
   id: events
+
+- name: Practice contests
+  url: /practice_contests
+  id: practice_contests

_data/practice_contests.yml

@@ -0,0 +1,79 @@
+# current categories: 
+# Dijkstra, Probability, BFS. Geometry, String hashing, 
+# Network flow, Segment trees, Dynamic programming, 
+# Searching, Interactive problems, Variety, NCPC
+
+- category: Dijkstra
+  links: [
+    https://open.kattis.com/contests/q5w4mr/problems
+  ]
+  
+- category: Probability
+  links: [
+    https://open.kattis.com/contests/dph9n8/problems
+  ]
+
+- category: BFS
+  links: [
+    https://open.kattis.com/contests/ezq4xe/problems
+  ]
+
+- category: Geometry
+  links: [
+    https://open.kattis.com/contests/gzdnab/problems
+  ]
+
+- category: String hashing
+  links: [
+    https://open.kattis.com/contests/ao629w/problems
+  ]
+
+- category: Network flow
+  links: [
+    https://open.kattis.com/contests/yyy5cb/problems
+  ]
+
+- category: Segment trees
+  links: [
+    https://open.kattis.com/contests/gay94k/problems
+  ]
+
+- category: Dynamic programming
+  links: [
+    https://open.kattis.com/contests/wvn2dn/problems
+  ]
+
+- category: Searching
+  links: [
+    https://open.kattis.com/contests/vu382t/problems
+  ]
+
+- category: Interactive problems
+  links: [
+    https://open.kattis.com/contests/rercsx/problems
+  ]
+
+- category: NCPC
+  links: [
+    https://open.kattis.com/contests/seutao/problems, 
+    https://open.kattis.com/contests/yjfiag/problems
+  ]
+
+- category: Variety
+  links: [
+    https://open.kattis.com/contests/pvfc9x/problems, 
+    https://open.kattis.com/contests/aq2iwc/problems, 
+    https://open.kattis.com/contests/pvfm44/problems, 
+    https://open.kattis.com/contests/bywt92/problems, 
+    https://open.kattis.com/contests/bjn3iq/problems,  
+    https://open.kattis.com/contests/tv7dur/problems, 
+    https://open.kattis.com/contests/gvnwpy/problems, 
+    https://open.kattis.com/contests/nuj5hf/problems, 
+    https://open.kattis.com/contests/z9d96w/problems, 
+    https://open.kattis.com/contests/esbxev/problems, 
+    https://open.kattis.com/contests/ggp7wr/problems, 
+    https://open.kattis.com/contests/gfcpf6/problems, 
+    https://open.kattis.com/contests/i2yhpu/problems, 
+    https://open.kattis.com/contests/t24oan/problems, 
+    https://open.kattis.com/contests/qp8fwm/problems
+  ]

practice_contests.md

@@ -0,0 +1,23 @@
+---
+layout: panel
+title: Practice contests
+id: practice_contests
+---
+
+## Past practice contests
+
+Here you can find a collection of some of the past practice contests we have held, sorted by the algorithm, technique or general theme they focused on.
+
+{% assign sorted_categories = site.data.practice_contests | sort: "category" %}
+
+{% for category in sorted_categories %}
+
+### {{ category.category }}
+
+<ul>
+    {% for link in category.links %}
+        <li><a href="{{link}}">{{ link }}</a></li>
+    {% endfor %}    
+</ul>
+
+{% endfor %}