feat(0128_longest-consecutive-sequence): add py3 solution

0128_longest-consecutive-sequence/README.md

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+Given an unsorted array of integers `nums`, return _the length of the longest consecutive elements sequence._
+
+You must write an algorithm that runs in `O(n)` time.
+
+**Example 1:**
+
+    Input: nums = [100,4,200,1,3,2]
+    Output: 4
+    Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
+    
+
+**Example 2:**
+
+    Input: nums = [0,3,7,2,5,8,4,6,0,1]
+    Output: 9
+    
+
+**Constraints:**
+
+*   `0 <= nums.length <= 105`
+*   `-109 <= nums[i] <= 109`

0128_longest-consecutive-sequence/python3/nlogn.py

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+# Time: O(NlogN)
+# Space: O(1)
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        nums.sort()
+        
+        max_length = 1
+        l = 1
+        
+        # We don't want to go OOB
+        for i in range(0, len(nums) - 1):
+            diff = nums[i + 1] - nums[i]
+            
+            # All good, still consecutive.
+            if diff == 1:
+                l += 1
+                max_length = max(max_length, l)
+            # We skip to next iteration of loop if
+            # item repeats. Otherwise, we reset
+            # running length variable to 1
+            elif diff != 0:
+                l = 1
+        
+        return max_length if len(nums) > 0 else 0