[leetcode]78. Subsets(Java)

最新推荐文章于 2022-10-07 09:01:27 发布

原创最新推荐文章于 2022-10-07 09:01:27 发布 · 1.1k 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#Subsets #leetcode

leetcode 专栏收录该内容

130 篇文章

订阅专栏

本文介绍了一种生成给定整数数组所有可能子集的算法实现。通过对递归方法的应用，确保了子集不包含重复元素，并提供了两种不同场景下的代码示例：一种是结果无需排序的情况，另一种是对结果进行了排序。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

https://leetcode.com/problems/subsets/#/description

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],
  []
]

package go.jacob.day629;

import java.util.ArrayList;
import java.util.List;

public class Demo3 {
	/*
	 * Runtime: 2 ms.Your runtime beats 30.58 % of java submissions.
	 * 牛客网和leetcode的区别是是否对结果进行排序
	 */
	public List<List<Integer>> subsets(int[] nums) {
		List<List<Integer>> res = new ArrayList<List<Integer>>();
		if (nums == null || nums.length < 1)
			return res;
		ArrayList<Integer> list = new ArrayList<Integer>();
		find(res, nums, list, 0);

		return res;
	}

	private void find(List<List<Integer>> res, int[] nums, ArrayList<Integer> list, int start) {
		res.add(new ArrayList<Integer>(list));
		if (start >= nums.length)
			return;
		for (int i = start; i < nums.length; i++) {
			list.add(nums[i]);

			find(res, nums, list, i + 1);
			list.remove(list.size() - 1);
		}
	}

}

再贴一个牛客网运行通过的。除了需要自定义比较器，其他解法相同

https://www.nowcoder.com/questionTerminal/c333d551eb6243e0b4d92e37a06fbfc9

package go.jacob.day629;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;

/**
 * @author Jacob
 */
public class Demo4 {
	/*
	 * Runtime: 2 ms.Your runtime beats 30.58 % of java submissions.
	 * 该题和leetcode的区别是是否对结果进行排序
	 */
	public ArrayList<ArrayList<Integer>> subsets(int[] nums) {
		ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
		if (nums == null || nums.length < 1)
			return res;
		Arrays.sort(nums);
		ArrayList<Integer> list = new ArrayList<Integer>();
		find(res, nums, list, 0);
		// 对结果进行排序，自定义比较器
		Collections.sort(res, new Comparator<ArrayList<Integer>>() {

			@Override
			public int compare(ArrayList<Integer> o1, ArrayList<Integer> o2) {
				int size1 = o1.size(), size2 = o2.size();
				if (size1 != size2)
					return size1 - size2;
				else {
					for (int i = 0; i < o1.size(); i++) {
						if (o1.get(i) == o2.get(i))
							continue;
						else
							return o1.get(i) - o2.get(i);
					}
				}
				return 0;
			}
		});

		return res;
	}

	private void find(ArrayList<ArrayList<Integer>> res, int[] nums, ArrayList<Integer> list, int start) {
		res.add(new ArrayList<Integer>(list));
		if (start >= nums.length)
			return;
		for (int i = start; i < nums.length; i++) {
			list.add(nums[i]);

			find(res, nums, list, i + 1);
			list.remove(list.size() - 1);
		}
	}

}