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Author: hogan-tech

0078-subsets/0078-subsets.py

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+# time complexity: O(n*2^n)
+# space complexity: O(n)
+from itertools import chain, combinations
+from typing import List
+
+
+class Solution:
+    def subsets(self, nums: List[int]) -> List[List[int]]:
+        result = []
+
+        def backtrack(start: int, comb: List[int]):
+            result.append(list(comb))
+            for i in range(start, len(nums)):
+                comb.append(nums[i])
+                backtrack(i + 1, comb)
+                comb.pop()
+
+        backtrack(0, [])
+        return result
+
+# time complexity: O(n*2^n)
+# space complexity: O(n*2^n)
+class Solution:
+    def subsets(self, nums):
+        result = [[]]
+        for num in nums:
+            newSubsets = []
+            for curr in result:
+                temp = curr.copy()
+                temp.append(num)
+                newSubsets.append(temp)
+            for curr in newSubsets:
+                result.append(curr)
+        return result
+
+# time complexity: O(n*2^n)
+# space complexity: O(n)
+class Solution:
+    def subsets(self, nums: List[int]) -> List[List[int]]:
+        n = len(nums)
+        result = []
+
+        for i in range(2**n, 2 ** (n + 1)):
+            # generate bitmask, from 0..00 to 1..11
+            bitmask = bin(i)[3:]
+            # append subset corresponding to that bitmask
+            result.append([nums[j] for j in range(n) if bitmask[j] == "1"])
+
+        return result
+
+
+class Solution:
+    def subsets(self, nums: List[int]) -> List[List[int]]:
+        result = list(chain.from_iterable(combinations(nums, r)
+                      for r in range(len(nums)+1)))
+        for i, item in enumerate(result):
+            result[i] = list(item)
+        return result
+
+
+class Solution:
+    def subsets(self, nums: List[int]) -> List[List[int]]:
+        output = [[]]
+        for num in nums:
+            output += [curr + [num] for curr in output]
+        return output
+
+
+nums = [1, 2, 3]
+print(Solution().subsets(nums))
+nums = [0]
+print(Solution().subsets(nums))