LeetCode 56 Merge Intervals - Problem Statement

Given an array of intervals, merge all overlapping intervals.

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

• [1,3] and [2,6] overlap (2 <= 3). Merge to [1,6].
• [8,10] and [15,18] don't overlap with anything.
• Result: [[1,6],[8,10],[15,18]].

With intervals = [[1,4],[4,5]]:

• [1,4] and [4,5] touch at endpoint 4. Consider them overlapping.
• Merge to [1,5].

Return the array of merged intervals.

Constraints: $1 \le$ intervals.length $\le 10^4$.