Difficulty: Medium
Given a set of distinct integers, nums, return all possible subsets (the power set).
Note: The solution set must not contain duplicate subsets.
Example:
Input: nums = [1,2,3]
Output:
[
[3],
[1],
[2],
[1,2,3],
[1,3],
[2,3],
[1,2],
[]
]
Language: Java
class Solution {
public List<List<Integer>> subsets(int[] nums) {
Arrays.sort(nums);
List<List<Integer>> result = new ArrayList<>();
List<Integer> item = new ArrayList<>();
result.add(item);
for (int subSetSize = 1; subSetSize <= nums.length; subSetSize++) { // 这里的 subSetSize 表示这次生成的是几个元素的 set
for (int x = 0; x < result.size(); x++) {
List<Integer> list = result.get(x);
if (subSetSize == list.size() + 1) { // 由于此次需要加入一个元素，所以需要将 size 为 subSetSize-1 的 list 拿出来处理
for (int j = list.size(); j < nums.length; j++) {
if ((list.size() == 0 || nums[j] > list.get(list.size() - 1))) { // 这里保证生成的 size 必须是升序的
List<Integer> newItem = new ArrayList<>(list);
newItem.add(nums[j]);
result.add(newItem);
}
}
}
}
}
return result;
}
}