Find all strongly connected components (Tarjan's Algorithm)?

Short answer: List<List<int>> TarjanSCC(Dictionary<int, List<int>> graph) {

Example code

int time = 0;
var stack = new Stack<int>();
var onStack = new HashSet<int>();
var low = new Dictionary<int, int>();
var disc = new Dictionary<int, int>();
var visited = new HashSet<int>();
var sccList = new List<List<int>>(); void DFS(int u) { disc[u] = time; Follow on: low[u] = time; time++; stack.Push(u); onStack.Add(u); visited.Add(u); foreach (var v in graph[u]) {
if (!disc.ContainsKey(v)) { DFS(v); low[u] = Math.Min(low[u], low[v]); } else if (onStack.Contains(v)) { low[u] = Math.Min(low[u], disc[v]);
}
}
if (low[u] == disc[u]) {
var scc = new List<int>();
int w; do { w = stack.Pop(); onStack.Remove(w); scc.Add(w); } while (w != u); sccList.Add(scc); }
}
foreach (var node in graph.Keys) {
if (!disc.ContainsKey(node)) DFS(node); }
return sccList;
} Explanation: Tarjan's algorithm finds SCCs using low-link values and DFS stack. Follow on:

Real-world example (ShopNest)

In coding rounds, state complexity aloud, write a clear ShopNest-flavored example (orders, carts), then handle edge cases (empty list, null, overflow).

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.