Method depthFirstSearch

java/0261-graph-valid-tree.java:26–42

(
        int node,
        int previous,
        Set<Integer> visited
    )

    }

    private boolean depthFirstSearch(
        int node,
        int previous,
        Set<Integer> visited
    ) {
        if (visited.contains(node)) return false;

        visited.add(node);

        for (var neighbor : adjacencyList.get(node)) {
            if (neighbor == previous) continue;

            if (!depthFirstSearch(neighbor, node, visited)) return false;
        }

        return true;
    }
}