Add PT2.java

Author: seanprashad

Miscellaneous/PT2.java

@@ -0,0 +1,102 @@
+import java.util.*;
+
+class AccessSystem {
+    Map<String, List<String>> children;
+    Map<String, String> parents;
+    Set<String> allRegions;
+    Map<String, Set<String>> grants;
+    Map<String, Set<String>> revokes;
+
+    public AccessSystem(String[][] edges) {
+        children = new HashMap<>();
+        parents = new HashMap<>();
+        allRegions = new HashSet<>();
+        grants = new HashMap<>();
+        revokes = new HashMap<>();
+
+        for (String[] edge : edges) {
+            String parent = edge[0], child = edge[1];
+
+            children.putIfAbsent(parent, new ArrayList<>());
+            children.get(parent).add(child);
+
+            parents.put(child, parent);
+
+            allRegions.add(child);
+            allRegions.add(parent);
+        }
+    }
+
+    public void grantAccess(String advertiserId, String regionId) {
+        if (!allRegions.contains(regionId)) {
+            return;
+        }
+
+        List<String> allSubRegions = getAllSubRegions(regionId);
+
+        grants.putIfAbsent(advertiserId, new HashSet<>());
+        revokes.putIfAbsent(advertiserId, new HashSet<>());
+
+        for (String region : allSubRegions) {
+            grants.get(advertiserId).add(region);
+            revokes.get(advertiserId).remove(region);
+        }
+    }
+
+    public void revokeAccess(String advertiserId, String regionId) {
+        if (!allRegions.contains(regionId)) {
+            return;
+        }
+
+        List<String> allSubRegions = getAllSubRegions(regionId);
+
+        grants.putIfAbsent(advertiserId, new HashSet<>());
+        revokes.putIfAbsent(advertiserId, new HashSet<>());
+
+        for (String region : allSubRegions) {
+            grants.get(advertiserId).remove(region);
+            revokes.get(advertiserId).add(region);
+        }
+    }
+
+    public boolean checkAccess(String advertiserId, String regionId) {
+        if (!allRegions.contains(regionId)) {
+            return false;
+        }
+
+        String curr = regionId;
+
+        Set<String> grantedRegions = grants.getOrDefault(advertiserId, Collections.emptySet());
+        Set<String> revokedRegions = revokes.getOrDefault(advertiserId, Collections.emptySet());
+
+        while (curr != null) {
+            if (revokedRegions.contains(curr)) { return false; }
+            if (grantedRegions.contains(curr)) { return true; }
+
+            curr = parents.get(curr);
+        }
+
+        return false;
+    }
+
+    private List<String> getAllSubRegions(String regionId) {
+        if (!allRegions.contains(regionId)) {
+            return Collections.emptyList();
+        }
+
+        List<String> result = new ArrayList<>();
+        Queue<String> q = new LinkedList<>();
+        q.offer(regionId);
+
+        while (!q.isEmpty()) {
+            String curr = q.poll();
+            result.add(curr);
+
+            for (String child : children.getOrDefault(curr, new ArrayList<>())) {
+                q.offer(child);
+            }
+        }
+
+        return result;
+    }
+}