return first pair whose sum is equal to given number

Author: ahsankamal

beginners/first_sum_of_pairs.rb

@@ -0,0 +1,59 @@
+# return the first pair starting from left whose sum is equal to given number
+# sum_pairs([10, 5, 2, 3, 7, 5], 10) => [3,7]
+# 				 ^-----------^
+# 					   ^--^ #[3,7] came earlier than [5,5]
+
+def sum_pairs(ints, sum)
+    hash = {}
+
+ints.each_with_index do |i,j|
+	 if hash[i].nil? 
+	 	hash[i]=[1,[j]]
+	 else
+	 	hash[i][0]+=1
+	 	hash[i][1]<<j
+	 end	
+	 end
+	 # print hash
+	 # puts ""
+
+min=10000000000
+tuple=nil
+ints.each do |i|
+	if hash[sum-i].nil? || hash[i].nil?
+		next
+	elsif sum-i == i 
+		if hash[i][0]>1 && min>hash[i][1][1]
+			min = hash[i][1][1]	
+			tuple = [i,i]
+			hash[i]=nil
+		end
+	elsif min>hash[sum-i][1][0]
+		min = hash[sum-i][1][0]
+		tuple = [i,sum-i]
+		hash[i]=nil
+		hash[sum-i]=nil
+	else
+		hash[i]=nil
+		hash[sum-i]=nil
+	end	
+	# print "#{min} #{tuple}\n"
+end
+tuple
+end
+
+print sum_pairs([1, 2, 3, 4, 1, 0], 2)
+print sum_pairs([1, 2, 3, 4, 2, 5, 7, 6, 7], 9)
+print sum_pairs([1, 2, 3, 4, 1, 4, 8, 9, 5], 8)
+
+
+# 
+# def sum_pairs(ints, s)
+#   seen = {}
+#   for i in ints do
+#     return [s-i, i] if seen[s-i]
+#     seen[i] = true
+#   end
+#   nil
+# end
+#