Subsets solution

Author: joshguha

78_subsets.py

@@ -0,0 +1,58 @@
+class Solution(object):
+    # def subsets(self, nums):
+    #     """
+    #     :type nums: List[int]
+    #     :rtype: List[List[int]]
+    #     """
+    #     nums.sort()
+    #     res = [[]]
+    #     res.append(list(nums))
+    #     for ls in range(1, len(nums)):
+    #         self.get_subsets(res, nums, [], ls, 0)
+    #     return res
+    #
+    # def get_subsets(self, res, nums, curr_set, ls, index):
+    #     # recursive
+    #     if ls == 0:
+    #         res.append(list(curr_set))
+    #     elif index < len(nums):
+    #         curr_set.append(nums[index])
+    #         self.get_subsets(res, nums, curr_set, ls - 1, index + 1)
+    #         curr_set.pop()
+    #         self.get_subsets(res, nums, curr_set, ls, index + 1)
+
+    # def subsets(self, nums):
+    #     # https://leetcode.com/discuss/89343/c-8-lines-bit-operation
+    #     # doesn't work when len(nums) > 32
+    #     nums.sort()
+    #     res = []
+    #     for i in range(1 << len(nums)):
+    #         res.append(self.get_subsets(nums, i))
+    #     return res
+    #
+    # def get_subsets(self, nums, magic):
+    #     res = []
+    #     for i in range(len(nums)):
+    #         if (1 << i) & magic != 0:
+    #            res.append(nums[i])
+    #     return res
+
+    def subsets(self, nums):
+        # Sort and iteratively generate n subset with n-1 subset, O(n^2) and O(2^n)
+        nums.sort()
+        res = [[]]
+        for index in range(len(nums)):
+            size = len(res)
+            # use existing subsets to generate new subsets
+            for j in range(size):
+                curr = list(res[j])
+                curr.append(nums[index])
+                res.append(curr)
+        return res
+
+
+
+
+if __name__ == "__main__":
+    s = Solution()
+    print s.subsets([1,2,3])