Time: 35 ms (80.56%), Space: 14.1 MB (33.36%) - LeetHub

78-subsets/78-subsets.py

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+class Solution:
+    def subsets(self, nums: List[int]) -> List[List[int]]:
+        
+        # All subsets can be mapped to a binary number where
+        #   - the number is the same length as the list
+        #   - a 1 represents the number being in the list, 0 otherwise
+        
+        # Example:  nums = [1,2,3]
+        #   subsetBinary = 0 = 0b000 -> []
+        #                = 3 = 0b011 -> [2, 3]
+        #   (2 ** 3) - 1 = 7 = 0b111 -> [1, 2, 3]
+        
+        import math
+        powerSet = []
+        
+        for subsetBinary in range(2 ** len(nums)):
+            subset = []
+            
+            # Iterates exactly n times (where n is the number of 1s in the binary string)
+            while subsetBinary > 0:
+                indexOfFirst1 = -(math.floor(math.log2(subsetBinary)) + 1)
+                
+                subset.append(nums[indexOfFirst1])
+    
+                subsetBinary -= 2 ** (-indexOfFirst1 - 1)
+        
+            powerSet.append(subset)
+        
+        return powerSet