Detect Cycles in Task Graph

Problem

Given a directed graph of startup task dependencies, write a function that returns True if the graph contains a cycle and False otherwise. The input is a list of task names tasks and a list of directed edges dependencies, where each edge [a, b] means task a depends on task b.

Constraints

• 1 <= len(tasks) <= 10^5
• 0 <= len(dependencies) <= 2 * 10^5
• Task names are unique strings
• Each dependency is a pair [task, prerequisite]
• A dependency may reference any task in tasks