Topological Sort (Dependency Ordering)

Given a directed graph with n nodes labeled 0..n-1 and m directed edges u -> v meaning u must be done before v, do the following: Determine whether a valid execution order exists (i.e., whether the graph is a DAG). If it exists, return any valid topological ordering (an array/list of length n). If it does not exist (there is a cycle), return an empty array/list. Input Line 1: integer n, number of nodes. Line 2: integer m, number of edges. Next m lines: two integers u v describing a directed edge u -> v. Output If a topological order exists: print n integers in one line representing a valid order. Otherwise: print nothing (or an empty line). Constraints 1 <= n <= 2 * 10^5 0 <= m <= 2 * 10^5 Node ids are in [0, n-1]. Target near-linear time, e.g. O(n+m). Example Input 4 3 0 1 1 2 0 3 Output 0 1 3 2