SummaryRanges

Problem

https://leetcode.com/problems/summary-ranges/

Solution

Note that subarray of consecutive numbers is a range. Iterate through the array and keep track of the start of the range. Keep iterating as long as the next element is consecutive. When the next element is not consecutive, create the range string based on whether the start equals the end.

Code

https://github.com/GeorgeRPu/tech-interview-prep/blob/main/solutions/SummaryRanges.py

from typing import List


def summaryRanges(nums: List[int]) -> List[str]:
    """Return the smallest sorted list of ranges that cover all the numbers in
    ``nums``.
    """
    summary_ranges = []

    i = 0
    while i < len(nums):
        start = nums[i]

        while i + 1 < len(nums) and nums[i] + 1 == nums[i + 1]:
            i += 1

        summary_ranges.append(get_range_str(start, nums[i]))
        i += 1

    return summary_ranges


def get_range_str(start, end):
    """Get the range from ``start`` to ``end`` as a formatted string.
    """
    return str(start) if start == end else f'{start}->{end}'

Test

>>> from SummaryRanges import summaryRanges
>>> summaryRanges([0, 1, 2, 4, 5, 7])
['0->2', '4->5', '7']
>>> summaryRanges([0, 2, 3, 4, 6, 8, 9])
['0', '2->4', '6', '8->9']

Functions

get_range_str(start, end)	Get the range from start to end as a formatted string.
summaryRanges(nums)	Return the smallest sorted list of ranges that cover all the numbers in nums.