Leetcode-78. Subsets

前言：为了后续的实习面试，开始疯狂刷题，非常欢迎志同道合的朋友一起交流。因为时间比较紧张，目前的规划是先过一遍，写出能想到的最优算法，第二遍再考虑最优或者较优的方法。如有错误欢迎指正。博主首发CSDN，mcf171专栏。

博客链接：mcf171的博客


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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],
[]
]

这个题目和77是类似的，我不由感叹递归大法好。。。Your runtime beats 91.55% of java submissions.
public class Solution {
public List<List<Integer>> subsets(int[] nums) {
List<List<Integer>> results = new ArrayList<List<Integer>>();
List<Integer> currentResults = new ArrayList<Integer>();
List<Integer> remain = new ArrayList<Integer>();
for(int num : nums) remain.add(num);

generate(results,currentResults,remain);
results.add(new ArrayList<Integer>());
return results;
}

public void generate(List<List<Integer>> results, List<Integer> currentResults, List<Integer> remain){

int times = remain.size();
for(int i = 0 ; i < times; i ++){
currentResults.add(remain.get(0));
remain.remove(0);
results.add(new ArrayList<Integer>(currentResults));
generate(results,currentResults,new ArrayList<Integer>(remain));
currentResults.remove(currentResults.size()-1);
}
}
}