tasks a-s

Task/Power-set/Java/power-set-1.java

@@ -0,0 +1,25 @@
+public static ArrayList<String> getpowerset(int a[],int n,ArrayList<String> ps)
+    {
+        if(n<0)
+        {
+            return null;
+        }
+        if(n==0)
+        {
+            if(ps==null)
+                ps=new ArrayList();
+            ps.add(" ");
+            return ps;
+        }
+        ps=getpowerset(a, n-1, ps);
+        ArrayList<String> tmp=new ArrayList<String>();
+        for(String s:ps)
+        {
+            if(s.equals(" "))
+                tmp.add(""+a[n-1]);
+            else
+                tmp.add(s+a[n-1]);
+        }
+        ps.addAll(tmp);
+        return ps;
+    }

Task/Power-set/Java/power-set-2.java

@@ -0,0 +1,23 @@
+public static <T> List<List<T>> powerset(Collection<T> list) {
+  List<List<T>> ps = new ArrayList<List<T>>();
+  ps.add(new ArrayList<T>());   // add the empty set
+
+  // for every item in the original list
+  for (T item : list) {
+    List<List<T>> newPs = new ArrayList<List<T>>();
+
+    for (List<T> subset : ps) {
+      // copy all of the current powerset's subsets
+      newPs.add(subset);
+
+      // plus the subsets appended with the current item
+      List<T> newSubset = new ArrayList<T>(subset);
+      newSubset.add(item);
+      newPs.add(newSubset);
+    }
+
+    // powerset is now powerset of list.subList(0, list.indexOf(item)+1)
+    ps = newPs;
+  }
+  return ps;
+}

Task/Power-set/Java/power-set-3.java

@@ -0,0 +1,16 @@
+public static <T extends Comparable<? super T>> LinkedList<LinkedList<T>> BinPowSet(
+		LinkedList<T> A){
+	LinkedList<LinkedList<T>> ans= new LinkedList<LinkedList<T>>();
+	int ansSize = (int)Math.pow(2, A.size());
+	for(Integer i= 0;i< ansSize;++i){
+		String bin= Integer.toString(i, 2); //convert to binary
+		while(bin.length() < A.size())bin = "0" + bin; //pad with 0's
+		LinkedList<T> thisComb = new LinkedList<T>(); //place to put one combination
+		for(int j= 0;j< A.size();++j){
+			if(bin.charAt(j) == '1')thisComb.add(A.get(j));
+		}
+		Collections.sort(thisComb); //sort it for easy checking
+		ans.add(thisComb); //put this set in the answer list
+	}
+	return ans;
+}