Power Set Using Recursion

recursion/Problems/PowerSetUsingRecursion.java

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+
+/*You are given a string. You need to print the lexicographically sorted power-set of the string.
+Note: The string s contains lowercase letter of alphabet.
+
+Example 1:
+
+Input:
+s = a
+Output: a
+Explanation: empty string and a 
+are only sets.
+Example 2:
+
+Input:
+s = abc
+Output: a ab abc ac b bc c
+Explanation: empty string, 
+a, ab, abc, ac, b, bc, c 
+are the sets.
+Your Task:
+You don't need to read input or print anything. You only need to complete the function powerSet that takes string s as parameter and returns a list of subsets. The lexicographic-sorting and printing is done automatically by the driver code.
+
+Expected Time Complexity: O(2|s|).
+Expected Auxiliary Space: O(|s|). 
+
+Constraints:
+1 <= |s| <= 10 */
+
+
+
+
+package recursion.Problems;
+
+import java.util.ArrayList;
+
+public class PowerSetUsingRecursion {
+    static ArrayList<String> powerSet(String s)
+    {
+        // add your code here
+       ArrayList<String> ls=new ArrayList<>();
+        getSet(s,"",0,s.length(),ls);
+        return ls;
+    }
+    public static void getSet(String s,String str,int i,int n,ArrayList<String> ls){
+        if(i==n){
+            ls.add(str);
+            return;
+        }
+        getSet(s,str,i+1,n,ls);
+        getSet(s,str+s.charAt(i),i+1,n,ls);
+    }
+}