Topological Sort for Task Scheduling

Problem: Task Dependency Ordering You are given n tasks numbered from 0 to n - 1, and an array prerequisites. Each dependency [a, b] means task b must be completed before task a. Return any valid order to complete all tasks. If no valid order exists because the dependency graph contains a cycle, return an empty array. Input Format The first line contains two integers n and m, the number of tasks and dependencies. The next m lines each contain two integers a and b, meaning a depends on b. Output Format If a valid order exists, print n integers representing one valid ordering. If no valid order exists, print an empty line. Constraints 1 <= n <= 10^5 0 <= m <= 2 * 10^5 0 <= a, b < n Duplicate dependency edges may appear. Example 1 Input: 4 4 1 0 2 0 3 1 3 2 One valid output: 0 1 2 3 Another valid output: 0 2 1 3 Example 2 Input: 2 2 0 1 1 0 Output: Example Input 4 4 1 0 2 0 3 1 3 2 Output 0 1 2 3