Practice Problem 3

Practice Problem: Check if there is a directed path from node $a$ to node $b$. Input: $n$ nodes, $m$ edges, and a query $(a, b)$. Output: "YES" if $a$ can reach $b$, "NO" otherwise. Hint: Run SCC detection. If $a$ and $b$ are in the same SCC, answer is "YES" (mutual reachability).

If they are in different SCCs, check if there is a path from scc[a] to scc[b] in the condensation DAG using BFS or DFS. This is faster than running BFS from $a$ every time if you have multiple queries.