Add ruby solution for balanced brackets problem, fix minor grammar error in CONTRIBUTING.md

Author: jmera

CONTRIBUTING.md

@@ -8,7 +8,7 @@ To add a new problem to the repo, no solution needs to be present. Just add a fo
 
 ### Adding a new solution
 
-To add a new solution to the repo, add the solution to the correct language directory in the solutions directory. Make the solution file name match the the problem. If a solution already exists, but your solution is distinctly different to the current solution, place both solutions in a directory named after the problem. The file names should then accurately represent the type of solution used in each solution. If you must use multiple files for your solution, create a solution directory and another directory for your solution assets.
+To add a new solution to the repo, add the solution to the correct language directory in the solutions directory. Make the solution file name match the problem. If a solution already exists, but your solution is distinctly different to the current solution, place both solutions in a directory named after the problem. The file names should then accurately represent the type of solution used in each solution. If you must use multiple files for your solution, create a solution directory and another directory for your solution assets.
 
 ## Style Guide
 

solutions/ruby/balanced_brackets.rb

@@ -0,0 +1,10 @@
+def balanced_brackets(str)
+  brackets = { '(' => ')', '{' => '}', '[' => ']' }
+
+  arr = []
+  str.each_char do |c|
+    if brackets[c] then arr << c 
+    else return false if arr.size < 1 || (brackets.key(c) != arr.pop) end
+  end
+  arr.size == 0 ? true : false
+end