Question

How to find the length of the longest consecutive sequence of an unsorted list of integers in Python

Answer 1

def longest_consecutive(nums):
    if not nums:
        return 0

    num_set = set(nums)
    longest_streak = 0

    for num in num_set:
        # Check if it's the start of a sequence
        if num - 1 not in num_set:
            current_num = num
            current_streak = 1

            # Count the length of the sequence
            while current_num + 1 in num_set:
                current_num += 1
                current_streak += 1

            longest_streak = max(longest_streak, current_streak)

    return longest_streak

nums = [680, 4, 590, 3, 1, 2]

print("Length of the longest consecutive sequence:", longest_consecutive(nums))  



'''
run:

Length of the longest consecutive sequence: 41010

'''

 

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