LeetCode-in-Java
491. Increasing Subsequences
Medium
Given an integer array nums, return all the different possible increasing subsequences of the given array with at least two elements. You may return the answer in any order.
The given array may contain duplicates, and two equal integers should also be considered a special case of increasing sequence.
Example 1:
Input: nums = [4,6,7,7]
Output: [[4,6],[4,6,7],[4,6,7,7],[4,7],[4,7,7],[6,7],[6,7,7],[7,7]]
Example 2:
Input: nums = [4,4,3,2,1]
Output: [[4,4]]
Constraints:
1 <= nums.length <= 15-100 <= nums[i] <= 100
Solution
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
@SuppressWarnings("java:S5413")
public class Solution {
public List<List<Integer>> findSubsequences(int[] nums) {
if (nums == null || nums.length == 1) {
return new ArrayList<>();
}
Set<List<Integer>> answer = new HashSet<>();
List<Integer> list = new ArrayList<>();
return new ArrayList<>(backtracking(nums, 0, list, answer));
}
private Set<List<Integer>> backtracking(
int[] nums, int start, List<Integer> currList, Set<List<Integer>> answer) {
if (currList.size() >= 2) {
answer.add(new ArrayList<>(currList));
}
for (int i = start; i < nums.length; i++) {
if (currList.isEmpty() || currList.get(currList.size() - 1) <= nums[i]) {
currList.add(nums[i]);
backtracking(nums, i + 1, currList, answer);
currList.remove(currList.size() - 1);
}
}
return answer;
}
}