#0255

Merge Overlapping Intervals

MediumDSA28 min20 XP

Problem

Given intervals [start, end], merge all overlapping intervals. Treat [1, 4] and [4, 5] as mergeable because they touch.

Why This Matters

Merging intervals is the base skill behind calendars, timeline cleanup, booking systems, and sweep-line problems.

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

Return the exact requested value.
Handle edge cases cleanly.
Use the intended DSA pattern when brute force would scale poorly.

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 []

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 []

Visible browser tests run here when available.

Testcases2 visible / 3 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 endpoints

Input[[1,4],[4,5]]

Expected[[1, 5]]

Touching intervals merge in this prompt.

Hidden Test Categories

empty interval listalready merged intervalsfully nested intervals