Problem Description

You are provided with a list of integer intervals, intervals, where each interval is represented as [start, end]. It is guaranteed that start <= end for all intervals, and the intervals are inclusive.

Your primary task is to identify and return all "gaps" or missing ranges between the covered portions of the number line. Two intervals are considered to "touch" if there is no missing integer between them (e.g., [1,3] and [4,6] touch because 3 and 4 are consecutive integers).

More precisely, the process involves:

1. Determining the union of all given intervals.
2. Identifying minCovered as the smallest integer covered by any interval in the union, and maxCovered as the largest integer covered by any interval in the union.
3. Returning a list of all maximal missing integer ranges within the overall span [minCovered, maxCovered] that are not covered by the union.

The output should be a list of disjoint intervals [gapStart, gapEnd] (inclusive), sorted by gapStart.

Example

Input: [[1,3],[7,10],[2,4]]

• The covered union is [1,4] ∪ [7,10].
• The overall span [minCovered, maxCovered] is [1,10].
• The gaps within [1,10] are [[5,6]]. Output: [[5,6]]

Notes and Edge Cases

• If the union of intervals is already contiguous (meaning there are no gaps), an empty list [] should be returned.
• Overlapping intervals should be merged and not create gaps.
• The input intervals list may be unsorted.

Constraints

• The number of intervals len(intervals) will be between 1 and 2 * 10^5.
• Interval endpoints will fit within a 32-bit signed integer.