Add ruby solution for array pair sum, made minor change to balanced brac...

solutions/ruby/array_pair_sum.rb

@@ -0,0 +1,15 @@
+def array_pair_sum(sum, arr)
+  result = []
+  seen = Hash.new(false)
+  while elem = arr.shift
+    target = sum - elem
+    (seen[elem] || seen[target]) ? next : (seen[elem] = true)
+    result << [elem, target] if arr.include?(target)
+  end
+  result
+end
+
+alias :f :array_pair_sum
+
+puts f(10, [3, 4, 5, 6, 7]).to_s # => [[3, 7], [4, 6]]
+puts f(8, [3, 4, 5, 4, 4]).to_s  # => [[3, 5], [4, 4]]

solutions/ruby/balanced_brackets.rb

@@ -6,5 +6,5 @@ def balanced_brackets(str)
     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
+  arr.empty?
 end