LeetCode-491. Increasing Subsequences

Given an integer array, your task is to find all the different possible increasing subsequences of the given array, and the length of an increasing subsequence should be at least 2 .

Example:
Input: [4, 6, 7, 7]
Output: [[4, 6], [4, 7], [4, 6, 7], [4, 6, 7, 7], [6, 7], [6, 7, 7], [7,7], [4,7,7]]
Note:
The length of the given array will not exceed 15.
The range of integer in the given array is [-100,100].
The given array may contain duplicates, and two equal integers should also be considered as a special case of increasing sequence.

package solutions._491;import java.util.*;/** * 491. Increasing Subsequences */class Solution {    // 标记是否被访问过    private boolean visited[];    private Set<List<Integer>> result;    private LinkedList<Integer> cur;    private int len;    private void DFS(int[] nums, int i) {        // 遍历到最后一个元素则跳出        if (i == nums.length) {            cur.clear();            return;        }        // 超过两个元素则加入结果集中        if (len >= 2) {            List<Integer> list = new ArrayList<>();            Object[] objects = cur.toArray();            for (int j = objects.length - 1; j >= 0; j--) {                list.add((Integer) objects[j]);            }            result.add(list);        }        for (int j = i + 1; j < nums.length; j++) {            if (!visited[j] && (nums[j] >= cur.peek())) {                visited[j] = true;                cur.push(nums[j]);                len++;                DFS(nums, j);                // 回溯                cur.pop();                visited[j] = false;                len--;            }        }    }    public List<List<Integer>> findSubsequences(int[] nums) {        visited = new boolean[nums.length];        result = new HashSet<>();        cur = new LinkedList<>();        for (int i = 0; i < nums.length; i++) {            visited[i] = true;            cur.clear();            cur.push(nums[i]);            len = 1;            DFS(nums, i);        }//        result.forEach(System.out::println);        List<List<Integer>> lists = new ArrayList<>();        lists.addAll(result);        return lists;    }    public static void main(String[] args) {        Solution solution = new Solution();        int[] arr = {1,2,3,4,5,6,7,8,9,10,1,1,1,1,1};        List<List<Integer>> list = solution.findSubsequences(arr);        System.out.println(list);    }}