Longest Consecutive Sequence LeetCode problem

data_structures/arrays/longest_consecutive_sequence.py

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+"""
+author: Sarthak Sharma https://github.com/Sarthak950
+Website: https://sarthak950.netlify.app
+date:   4 OCT 2023
+Longest Consecutive Sequence Problem from LeetCode
+"""
+
+
+def longest_consecutive_sequence(nums: list[int]) -> int:
+    """
+    Finds the length of the longest consecutive sequence in a list of numbers.
+
+    Args:
+        nums (List[int]): A list of integers.
+
+    Returns:
+        int: The length of the longest consecutive sequence.
+
+    Examples:
+        >>> longest_consecutive_sequence([100, 4, 200, 1, 3, 2])
+        4
+        >>> longest_consecutive_sequence([1, 2, 3, 4, 5])
+        5
+        >>> longest_consecutive_sequence([5, 4, 3, 2, 1])
+        5
+        >>> longest_consecutive_sequence([])
+        0
+    """
+    if not nums:
+        return 0
+
+    # Create a set of all the numbers in the list
+    num_set = set(nums)
+    longest_sequence = 0
+
+    # Iterate over the set of numbers
+    for num in num_set:
+        # If the number that is one less than the current number is not in the set,
+        # then this is the beginning of a sequence
+        if num - 1 not in num_set:  # Start of a potential sequence
+            # Store the current number in a variable
+            # and initiate a sequence length counter
+            current_num = num
+            current_sequence = 1
+
+            # While the next number is in the set,
+            # increment the current number and the sequence counter
+            while current_num + 1 in num_set:
+                current_num += 1
+                current_sequence += 1
+
+            # Update the longest sequence if the current sequence is longer
+            longest_sequence = max(longest_sequence, current_sequence)
+
+    return longest_sequence
+
+
+"""
+This code takes in a list of numbers and returns the length of
+the longest sequence of consecutive numbers in the list.
+For example, if the list is [1, 3, 2, 4, 5, 6, 7], the function will return 5,
+since the longest sequence of consecutive numbers is [3, 4, 5, 6, 7].
+"""