Subsets backtracking

algorithms/Java/backtracking/subsets.java

@@ -0,0 +1,50 @@
+import java.util.List;
+import java.util.ArrayList;
+
+class Subsets {
+    // Given an integer array nums of unique elements, return all possible 
+    // subsets (the power set).
+    // The solution set must not contain duplicate subsets. Return the solution in any order.
+
+    static void dfs(
+            List<Integer> subset,          
+            List<List<Integer>> subsets,   
+            int[] nums,                   
+            int i                        
+    ) {
+        // Base case: when we have processed all elements in the array
+        if (i == nums.length) {
+            // Add the current subset to the list of subsets
+            subsets.add(new ArrayList<>(subset));
+            return;
+        }
+
+        // Include the current element in the subset
+        subset.add(nums[i]);
+
+        // Recursively generate subsets including the current element
+        dfs(subset, subsets, nums, i + 1);
+
+        // Backtrack: Remove the last element to explore subsets without it
+        subset.remove(subset.size() - 1);
+
+        // Recursively generate subsets without the current element
+        dfs(subset, subsets, nums, i + 1);
+    }
+
+    static List<List<Integer>> subsets(int[] nums) {
+        List<List<Integer>> subsets = new ArrayList<>();
+
+        dfs(new ArrayList<>(), subsets, nums, 0);
+
+        return subsets;
+    }
+
+    public static void main(String[] args) {
+        // Example usage
+        System.out.println(subsets(new int[]{1, 2, 3}));
+        System.out.println(subsets(new int[]{0}));
+
+        // time complexity is : O(2^n) where n is the size of input array
+    }
+}