Common SCC Mistakes

Common mistake in Kosaraju: forgetting to reset the visited array between the two DFS passes. If you do not reset, the second pass will not visit any nodes. Common mistake in Tarjan: updating low[v] with disc[u] even when $u$ is not on the current stack.

Only update low[v] if $u$ is still on the stack (use an $on\_stack$ array). Debug tip: Trace your algorithm by hand on a small graph ($4$-$5$ nodes). Print $disc$, $low$, and stack contents at each step. Compare with expected output.