#0034

Merge Overlapping Intervals

MediumDSA20 min15 XP

Problem

Given intervals [start, end], merge all overlapping intervals and return the merged list sorted by start.

Why This Matters

Intervals show up in calendars, booking systems, logs, timelines, and scheduling interviews.

Function Signature

def merge_intervals(intervals):

Examples

Example 1

Inputintervals = [[1,3], [2,6], [8,10], [15,18]]

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

[1,3] and [2,6] overlap, so they become [1,6].

Constraints

Each interval has start <= end.
Input may be unsorted.
Touching intervals, like [1,3] and [3,5], should merge.

CodePython

def merge_intervals(intervals):
    """
    Input example: intervals = [[1,3], [2,6], [8,10], [15,18]]
    Return: [[1,6], [8,10], [15,18]]
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return intervals

def merge_intervals(intervals):
    """
    Input example: intervals = [[1,3], [2,6], [8,10], [15,18]]
    Return: [[1,6], [8,10], [15,18]]
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return intervals

Visible browser tests run here when available.

Testcases2 visible / 4 hidden categories

Classic overlap

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

Expected[[1,6], [8,10], [15,18]]

Only the first two intervals overlap.

Touching intervals

Input[[1,3], [3,5]]

Expected[[1,5]]

start <= previous end means the intervals connect.

Hidden Test Categories

Empty listAlready merged intervalsUnsorted intervalsOne interval contained inside another