Merge pull request neetcode-gh#2016 from MikeQCarr/longest-consecutiv…

…e-sequence

Update: 0128-longest-consecutive-sequence.rb

ruby/0128-longest-consecutive-sequence.rb

@@ -1,52 +1,14 @@
 def longest_consecutive(nums)
-  return 0 if nums.empty?
-
-  hash = {}
-  nums.each { |num| hash[num] = true }
-  longest = 0
-  nums.each do |num|
-    next if hash[num - 1]
-
-    challenger = 1
-    loop do
-      if hash[num + challenger]
-        challenger += 1
-      else
-        break
-      end
-    end
-    longest = challenger if challenger > longest
-  end
-
-  longest
-end
-
-# Another way to do it.
-def longest_consecutive(nums)
-  return 0 if nums.empty?
-
-  hash = {}
-  nums.each { |num| hash[num] = -1 }
-  nums.each do |num|
-    next unless hash[num] == -1
-
-    longest_consec = 1
-    loop do
-      val = hash[num + longest_consec]
-      case val
-      when -1
-        hash[num + longest_consec] = -2
-        longest_consec += 1
-      when nil
-        hash[num] = longest_consec
-        break
-      else
-        longest_consec += hash[num + longest_consec]
-        hash[num] = longest_consec
-        break
-      end
+    set = Set.new(nums)
+    set.reduce(0) do |longest, num|
+        if !set.include?(num-1)
+            length = 0
+            while set.include?(num + length) do
+                length += 1
+            end
+            next(longest > length ? longest : length)
+        end
+
+        longest
     end
-  end
-
-  hash.max_by { |_k, v| v }[1]
 end