Day 2 - added complete Ruby solution and updated README.md file

Author: mikasjp

02/solution.rb

@@ -1,12 +1,26 @@
-data = File.open("data.txt")
+DATA = File.open("data.txt")
     .read()
     .split
 
 # First part
-c =  data.map{|row| row.split("")}
+c =  DATA.map{|row| row.split("")}
             .map{|row| row.uniq.map{ |char| row.count(char) if [2, 3].include? row.count(char) }.compact.uniq}
             .reduce([], :concat)
 
 puts "First part: " + c.uniq
         .map{|x| c.count(x)}
-        .inject(:*).to_s
+        .inject(:*).to_s
+
+# Second part
+
+def hamming(p)
+    h = p[0].split("").zip(p[1].split("")).map{|p| p.first==p.last}
+    return h.count(FALSE), h.each_with_index.select{|v,i| v==FALSE}.map{|p| p[1]}
+end
+
+puts "Second part: " + DATA.combination(2)
+            .map{ |p| [p[0], hamming(p)[1]] if hamming(p)[0]==1 }
+            .compact
+            .map{|p| p.first.split("").each_with_index.select{|v,i| i!=p.last.last}.map{|q| q[0]}}
+            .first
+            .join("")

README.md

@@ -7,12 +7,13 @@ Just for practice and fun. Thank You [Eric](http://was.tl/)!
 | Day   | Name                                 | Python                     | Ruby                       |
 | :---: | :----------------------------------- | :------------------------: | :------------------------: |
 | 01    | [Chronal Calibration][day01]         | [:heavy_check_mark:][py01] | [:heavy_check_mark:][rb01] |
-| 02    | [Inventory Management System][day02] | [:heavy_check_mark:][py02] |                            |
+| 02    | [Inventory Management System][day02] | [:heavy_check_mark:][py02] | [:heavy_check_mark:][rb02] |
 
 [py01]: ./01/solution.py
 [py02]: ./02/solution.py
 
 [rb01]: ./01/solution.rb
+[rb02]: ./02/solution.rb
 
 [day01]: https://adventofcode.com/2018/day/1
 [day02]: https://adventofcode.com/2018/day/2