leetcode : subsets
Given a set of distinct integers, nums, return all possible subsets.
Note: 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], [] ]
思路: 深度优先, 回溯剪枝 dfs backtracking
public class Solution { public List<List<Integer>> subsets(int[] nums) { List<List<Integer>> result = new ArrayList<List<Integer>>(); if(nums == null || nums.length == 0){ return result; } List<Integer> list = new ArrayList<Integer>(); dfs(result, list, nums, 0); return result; } public void dfs(List<List<Integer>> result, List<Integer> list,int[] nums, int position){ if(position > nums.length){ return; } result.add(new ArrayList<Integer>(list)); for(int i = position; i < nums.length; i++){ list.add(nums[i]); dfs(result, list, nums, i + 1); list.remove(list.size() - 1); } } }