#0253

Course Schedule

MediumDSA28 min20 XP

Problem

There are num_courses courses labeled 0 to num_courses - 1. Each prerequisite [a, b] means b must be taken before a. Return True if all courses can be finished.

Why This Matters

Topological sorting is how you reason about dependency graphs in courses, builds, workflows, and task schedulers.

Function Signature

def can_finish(num_courses, prerequisites):

Examples

Example 1

Inputnum_courses = 2, prerequisites = [[1, 0]]

OutputTrue

Take course 0 first, then course 1.

Constraints

Return the exact requested value.
Handle empty or small inputs when the prompt allows them.
Prefer the target DSA pattern over brute force when the input can grow.

CodePython

def can_finish(num_courses, prerequisites):
    """
    Input example: num_courses = 2, prerequisites = [[1, 0]]
    Return: True
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return True

def can_finish(num_courses, prerequisites):
    """
    Input example: num_courses = 2, prerequisites = [[1, 0]]
    Return: True
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return True

Visible browser tests run here when available.

Testcases2 visible / 3 hidden categories

Simple dependency

Input2 courses, [[1, 0]]

ExpectedTrue

No cycle exists.

Cycle

Input2 courses, [[1,0],[0,1]]

ExpectedFalse

Each course waits for the other.

Hidden Test Categories

disconnected courseslong chainself prerequisite