【LeetCode OJ】Longest Consecutive Sequence

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class
Solution:

    # @param num, a list of integer

    # @return an integer

    def
longestConsecutive(self, num):

        """

        Find the longest consecutive number sequence by using hash map

        1) Add all numbers in the list to a hash set HS

        2) Let max_length = 0, which records the length of the current longest consecutive sequence

        3) For each number n in the hash set

                count the number of all n‘s left consecutive numbers in the hash set

                count the number of all n‘s right consecutive numbers in the hash set

                remove the counted numbers from the hash set

          Update the max_length with the length of this consecutive sequence contaning n.

        """

        # Conver the list to a hash set, this will remove the duplicates

        numbers =
set(num)

        # Current max_len

        max_len =
0

        while
numbers:

            # Get a number from the hash set

            x =
numbers.pop()

            # This sequence only containing x is length of 1

            x_len =
1

            # Find all left consecutive numbers of x

            left =
x-1

            while
left in
numbers:

                numbers.remove(left)

                left -=
1

            # Find all right consecutive numbers of x

            right =
x+1

            while
right in
numbers:

                numbers.remove(right)

                right +=
1

            # Update the max_len

            max_len =
max(max_len, right-left-1)

        return
max_len