Merge Intervals Python Solution with Tests

lcpy gen -n 56   # by problem number
lcpy gen -s merge_intervals   # by problem name

Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]

Input: intervals = [[1,4],[4,5]]
Output: [[1,5]]

Input: intervals = [[4,7],[1,4]]
Output: [[1,7]]

class Solution:
    # Time: O(n log n)
    # Space: O(1)
    def merge(self, intervals: list[list[int]]) -> list[list[int]]:
        intervals.sort()
        merged = [intervals[0]]

        for start, end in intervals[1:]:
            if start <= merged[-1][1]:
                merged[-1][1] = max(merged[-1][1], end)
            else:
                merged.append([start, end])

        return merged