Merge Intervals

Problem

Merge all overlapping intervals and return the condensed result.

Example 1

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

Constraints

• 1 <= intervals.length <= 10^4

Notes

• Focus on the underlying intervals pattern.
• Write the cleanest correct solution before optimizing further.
• Hidden tests cover larger edge cases than the visible examples.