【LeetCode】 491. Increasing Subsequences

最新推荐文章于 2025-01-18 01:32:59 发布

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最新推荐文章于 2025-01-18 01:32:59 发布

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本文介绍了一种算法，用于从给定整数数组中找出所有不同的递增子序列，子序列长度至少为2。示例输入为[4,6,7,7]，输出包括[[4,6],[4,7],[4,6,7],[4,6,7,7],[6,7],[6,7,7],[7,7],[4,7,7]]等。文章提供了完整的Java实现代码。

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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.

public class Solution {
    public List<List<Integer>> findSubsequences(int[] nums) {
        Set<List<Integer>> res = new HashSet<List<Integer>>();
        helper(res, new ArrayList<Integer>(), nums, 0);
        return new ArrayList<List<Integer>>(res);
    }
    
    private void helper(Set<List<Integer>> res, List<Integer> subList, int[] nums, int start) {
        if (subList.size() >= 2) {
            res.add(new ArrayList<Integer>(subList));
        }
        for (int i = start; i < nums.length; i++) {
            if (subList.size() == 0 || subList.get(subList.size() - 1) <= nums[i]) {
                subList.add(nums[i]);
                helper(res, subList, nums, i + 1);
                subList.remove(subList.size() - 1);
            }
        }
    }
}