Adding a sheet for Distributed Systems (dipakkr#673)

* Adding to contributors.md

* Starting a sheet for Distributed Systems

CONTRIBUTORS.md

@@ -246,6 +246,7 @@ Instructions :
 | 215 | **William Cook** | United States | Software Engineer | [Github](https://github.com/bcookdev) |
 | 216 | **Leoberto J. Preuss Jr.** | Brazil | Technical Writer | [GitHub](https://github.com/leoberto)|
 | 216 | **Rakesh Kumar** | India | Software Developer | [GitHub](https://github.com/rkamn)|
+| 217 | **Prakhar** |  -  | CS | [GitHub](https://github.com/prakhar0409) |
 
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DistributedSystems.md

@@ -0,0 +1,38 @@
+## Distributed Systems Cheet Sheet
+
+### Gossiping, P2P Networks, DHTs
+
+ - Epidemic Based Algorithms
+ - Gossip Based Algorithms
+ - Napster
+ - Gnutella
+ - Pastry DHT
+ - Chord DHT
+ - Freenet
+ - BitTorrent
+
+### Distributed Algorithms
+
+ - Ordering of Events in a Distributed System
+ - Lamport's Mutual Exclusion Algorithm
+ - Ricart Agarwala Algorithm
+ - Token based Mutual Exclusion
+ - Leader Election
+ - Minimum Spanning Tree
+ - Paxos
+ - 2-Phase Commit
+ - 3-Phase Commit
+
+### Practical Systems
+
+ - Map Reduce
+ - Hadoop
+ - Google File System
+ - Google Percolator
+ - Amazon Dynamo
+ - Coda
+ - AFS and NFS
+ - Corona
+ - Condor
+ - Cassandra
+ - Hbase/Bigtable