78. Subsets java solutions

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],
  []
]

public class Solution {
    List<List<Integer>> ans = new ArrayList<>();
    public List<List<Integer>> subsets(int[] nums) {
        List<Integer> list = new ArrayList<>();
        ans.add(list);
        for(int i = 0; i < nums.length; i++){//按照 取subset的长度 一个个遍历一遍
            findSubset(list,nums,i+1,0);
        }
        return ans;
    }
    
    public void findSubset(List<Integer> list, int[] nums, int k, int s){
        if(k == 0){
            List<Integer> tmp = new ArrayList<>(list);
            ans.add(tmp);
            return;
        }
        for(int i = s; i < nums.length; i++){
            list.add(nums[i]);
            findSubset(list,nums,k-1,i+1);
            list.remove(list.size()-1);
        }
    }
}

一个小的总结帖，二刷再试下其他解法。

https://discuss.leetcode.com/topic/46159/a-general-approach-to-backtracking-questions-in-java-subsets-permutations-combination-sum-palindrome-partitioning