Merge Intervals

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Problem

Given an array of intervals, merge all overlapping intervals and return an array of the non-overlapping intervals that cover all the intervals in the input.

Examples

Example 1

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

Output:[[1,6],[8,10],[15,18]]

Example 2

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

Output:[[1,5]]

Constraints

1 <= intervals.length <= 10^4

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How to approach it: the Intervals pattern

Problems about ranges — meeting times, event schedules, ranges on a number line — almost always start with sorting the intervals by start (or end) time, then sweeping through them once.

Look for this pattern when

The problem talks about meetings, bookings, ranges, or scheduling.
You need to merge overlapping ranges, find gaps, or count how many overlap at once.

Read the full Intervals guide →

Video walkthroughs

Original problem on LeetCode ↗