Java for LeetCode 078 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],
  []
]

解题思路：

和上题十分相似，修改上题代码即可，JAVA实现如下：

    static public List<List<Integer>> subsets(int[] nums) {
    	List<List<Integer>> list = new ArrayList<List<Integer>>();
    	list.add(new ArrayList<Integer>());
    	Arrays.sort(nums);
    	for(int i=1;i<=nums.length;i++)
    		dfs(list, nums.length, i, 0,nums,-1);
    	return list;
    }

	static List<Integer> alist = new ArrayList<Integer>();

	static void dfs(List<List<Integer>> list, int n, int k, int depth,int[] nums,int last) {
		if (depth >= k) {
			list.add(new ArrayList<Integer>(alist));
			return;
		}
		for (int i = last+1; i <= n-k+depth; i++) {
			alist.add(nums[i]);
			dfs(list, n, k, depth + 1,nums,i);
			alist.remove(alist.size() - 1);
		}
	}