import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.checkerframework.checker.nullness.qual.*;

public class MethodTypeVars3 {
  public static <@KeyFor("#1") T extends @KeyFor("#1") Object> Map<T, List<T>> dominators(
      Map<T, List<T>> preds) {
    List<T> nodes = new ArrayList<>(preds.keySet());

    // Compute roots & non-roots, for convenience
    List<@KeyFor("preds") T> roots = new ArrayList<>();
    List<@KeyFor("preds") T> non_roots = new ArrayList<>();

    Map<@KeyFor("preds") T, List<T>> dom = new HashMap<>();

    // Initialize result:  for roots just the root, otherwise everything
    for (@KeyFor("preds") T node : preds.keySet()) {
      if (preds.get(node).isEmpty()) {
        // This is a root
        roots.add(node);
        // Its only dominator is itself.
        Set<@KeyFor("preds") T> set = Collections.singleton(node);

        dom.put(node, new ArrayList<T>(set));

        dom.put(node, new ArrayList<T>(Collections.singleton(node)));
      } else {
        non_roots.add(node);
        dom.put(node, new ArrayList<T>(nodes));
      }
    }

    return dom;
  }

  <XXX extends Object> void test(Map<XXX, List<XXX>> dom, XXX node) {
    dom.put(node, new ArrayList<XXX>(Collections.singleton(node)));
  }
}