LeetCode題解：Subsets

LeetCode題解：Subsets

Given a set of distinct integers, nums, return all possible subsets.

Note:
Elements in a subset must be in non-descending order.
The solution set must not contain duplicate subsets.
For example,
If nums = [1,2,3], a solution is:

[
[3],
[1],
[2],
[1,2,3],
[1,3],
[2,3],
[1,2],
[]
]

題意：給定元素，返回所有可能的子集

解決思路：類似於求組合那題的思路，先添加一個數，然後插入第二個數的時候不斷復制

代碼：

public class Solution {
    public List> subsets(int[] nums) {
        List> result = new ArrayList>();

        int subsetNum = (int)Math.pow(2, nums.length);
        Arrays.sort(nums);

        for(int i = 0; i < subsetNum; i++){
            result.add(new ArrayList());
        }

        for(int i = 0; i < nums.length; i++){
            for(int j = 1; j < subsetNum; j++){
                List temp = result.get(j);

                if(((j >> i) & 1) == 1){
                    temp.add(nums[i]);
                }
            }
        }

        return result;
    }
}