【leetcode】78. subsets

1.题目描述

Given a set of distinct integers, nums, return all possible subsets (the power set).

给定一组不含重复元素的整数数组 nums,返回该数组所有可能的子集(幂集)。

Note: The solution set must not contain duplicate subsets.

说明:解集不能包含重复的子集。

Example:

Input: nums = [1,2,3]
Output:
[
[3],
[1],
[2],
[1,2,3],
[1,3],
[2,3],
[1,2],
[]
]

2.Solutions

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public List<List<Integer>> subsets(int[] nums) {
List<List<Integer>> list = new ArrayList<>();
Arrays.sort(nums);
backtrack(list, new ArrayList<>(), nums, 0);
return list;
}

private void (List<List<Integer>> list ,
List<Integer> tempList, int [] nums, int start){
list.add(new ArrayList<>(tempList));
for(int i = start; i < nums.length; i++){
tempList.add(nums[i]);
backtrack(list, tempList, nums, i + 1);
tempList.remove(tempList.size() - 1);
}
}

I drew an ugly but clear pic about how backtracking works. Once nums[i] arrived at end, remove the last element and go back to last level until all possible solutions are stored.

位运算:My solution using bit manipulation

(完)