class Solution {
public List<List<Integer>> subsets(int[] nums) {
//创建结果数组
List<List<Integer>> ans = new ArrayList<>();
//回溯
backtrack(0,nums,new ArrayList<Integer>() ,ans);
return ans;
}
//回溯方法
private void backtrack(int start,int[] nums,ArrayList<Integer> track,List<List<Integer>> ans){
//满足条件
ans.add(new ArrayList<> (track));
//做选择
for(int i = start;i < nums.length;i++){
//做选择；
track.add(nums[i]);
//回溯
backtrack(i+1,nums,track,ans);
//撤销选择
track.remove(track.size()-1);
}
}
}
