Merge pull request #175 from BrianLusina/feat/algorithms-backtracking-find-subsets

feat(algorithms, backtracking): find subsets

Author: BrianLusina

DIRECTORY.md

@@ -38,6 +38,11 @@
         * [Test Generate Permutations](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/backtracking/permutations/generate_permutations/test_generate_permutations.py)
     * Restore Ip Addresses
       * [Test Restore Ip Addresses](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/backtracking/restore_ip_addresses/test_restore_ip_addresses.py)
+    * Subsets
+      * Cascading Subsets
+        * [Test Cascading Subsets](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/backtracking/subsets/cascading_subsets/test_cascading_subsets.py)
+      * Find All Subsets
+        * [Test Find All Subsets](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/backtracking/subsets/find_all_subsets/test_find_all_subsets.py)
     * Word Search
       * [Constants](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/backtracking/word_search/constants.py)
       * [Point](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/backtracking/word_search/point.py)
@@ -307,11 +312,6 @@
   * Stack
     * Daily Temperatures
       * [Test Daily Temperatures](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/stack/daily_temperatures/test_daily_temperatures.py)
-  * Subsets
-    * Cascading Subsets
-      * [Test Cascading Subsets](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/subsets/cascading_subsets/test_cascading_subsets.py)
-    * Find All Subsets
-      * [Test Find All Subsets](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/subsets/find_all_subsets/test_find_all_subsets.py)
   * Taxi Numbers
     * [Taxi Numbers](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/taxi_numbers/taxi_numbers.py)
   * Top K Elements

algorithms/subsets/__init__.py …orithms/backtracking/subsets/__init__.pyalgorithms/subsets/__init__.py renamed to algorithms/backtracking/subsets/__init__.py algorithms/subsets/__init__.py renamed to algorithms/backtracking/subsets/__init__.py

@@ -1,6 +1,6 @@
 import unittest
 
-from algorithms.subsets.cascading_subsets import each_cons
+from algorithms.backtracking.subsets.cascading_subsets import each_cons
 
 
 class CascadingSubsetsTestCase(unittest.TestCase):

…thms/subsets/cascading_subsets/README.md …king/subsets/cascading_subsets/README.mdalgorithms/subsets/cascading_subsets/README.md renamed to algorithms/backtracking/subsets/cascading_subsets/README.md algorithms/subsets/cascading_subsets/README.md renamed to algorithms/backtracking/subsets/cascading_subsets/README.md

@@ -22,3 +22,20 @@ Given an array of integers, nums, find all possible subsets of nums, including t
 - Bit Manipulation
 - Backtracking
 - Arrays
+
+---
+# Subsets II
+
+Given an integer array nums, that can contain duplicate elements,  return all possible subsets while ensuring that each
+subset is unique. The output must include unique subsets, and you may return them in any order.
+
+## Constraints
+
+- 1 <= `nums.length` <= 10
+- -10 <= `nums[i]` <= 10
+
+## Examples
+
+![Example 1](images/examples/find_all_subsets_ii_example_1.png)
+![Example 2](images/examples/find_all_subsets_ii_example_2.png)
+![Example 3](images/examples/find_all_subsets_ii_example_3.png)

…ms/subsets/cascading_subsets/__init__.py …ng/subsets/cascading_subsets/__init__.pyalgorithms/subsets/cascading_subsets/__init__.py renamed to algorithms/backtracking/subsets/cascading_subsets/__init__.py algorithms/subsets/cascading_subsets/__init__.py renamed to algorithms/backtracking/subsets/cascading_subsets/__init__.py

@@ -0,0 +1,65 @@
+from typing import List
+
+
+def find_all_subsets(nums: List[int]) -> List[List[int]]:
+    n = len(nums)
+
+    if n == 0:
+        return []
+
+    subsets = []
+
+    def backtrack(first, curr):
+        # Add the current subset to the output
+        subsets.append(curr[:])
+        # Generate subsets starting from the current index
+        for i in range(first, n):
+            curr.append(nums[i])
+            backtrack(i + 1, curr)
+            curr.pop()
+
+    backtrack(0, [])
+    return subsets
+
+
+def find_all_subsets_with_duplicates(nums: List[int]) -> List[List[int]]:
+    n = len(nums)
+
+    if n == 0:
+        return []
+
+    # Sort in place to ensure that duplicate elements are next to each other, which will be used to skip over the duplicate
+    # elements in the iteration.
+    # Time complexity here is O(n log(n)) and space complexity is O(n) due to Timsort requiring space to handle sorting
+    # in place
+    nums.sort()
+
+    subsets: List[int] = []
+    result: List[List[int]] = []
+
+    def backtrack(idx: int) -> None:
+        """
+        Backtrack to create subsets from the given current index of the element being considered
+        Args:
+            idx(int): index of the element being considered.
+        """
+        # Base case, if we reach the end of the list, we include the current subset to the result
+        if idx == n:
+            result.append(subsets[:])
+            return
+
+        # Add the current subset to the output
+        # Include the current element to the subset and move to the next element
+        subsets.append(nums[idx])
+        backtrack(idx + 1)
+        # After recursion, remove it to backtrack and explore the excluded path
+        subsets.pop()
+
+        # Skip the current element(exclude path), but skip duplicates too. If there are duplicate elements, skip them all
+        # when choosing exclude path. This ensures that we only take one unique subset for each duplicate group
+        while idx + 1 < n and nums[idx] == nums[idx + 1]:
+            idx += 1
+        backtrack(idx + 1)
+
+    backtrack(0)
+    return result