Skip to content

491. Non-decreasing Subsequences

Description

Given an integer array nums, return all the different possible non-decreasing subsequences of the given array with at least two elements. You may return the answer in any order.

 

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

Solutions

Solution 1

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
class Solution:
    def findSubsequences(self, nums: List[int]) -> List[List[int]]:
        def dfs(u, last, t):
            if u == len(nums):
                if len(t) > 1:
                    ans.append(t[:])
                return
            if nums[u] >= last:
                t.append(nums[u])
                dfs(u + 1, nums[u], t)
                t.pop()
            if nums[u] != last:
                dfs(u + 1, last, t)

        ans = []
        dfs(0, -1000, [])
        return ans

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
class Solution {
    private int[] nums;
    private List<List<Integer>> ans;

    public List<List<Integer>> findSubsequences(int[] nums) {
        this.nums = nums;
        ans = new ArrayList<>();
        dfs(0, -1000, new ArrayList<>());
        return ans;
    }

    private void dfs(int u, int last, List<Integer> t) {
        if (u == nums.length) {
            if (t.size() > 1) {
                ans.add(new ArrayList<>(t));
            }
            return;
        }
        if (nums[u] >= last) {
            t.add(nums[u]);
            dfs(u + 1, nums[u], t);
            t.remove(t.size() - 1);
        }
        if (nums[u] != last) {
            dfs(u + 1, last, t);
        }
    }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
class Solution {
public:
    vector<vector<int>> findSubsequences(vector<int>& nums) {
        vector<vector<int>> ans;
        vector<int> t;
        dfs(0, -1000, t, nums, ans);
        return ans;
    }

    void dfs(int u, int last, vector<int>& t, vector<int>& nums, vector<vector<int>>& ans) {
        if (u == nums.size()) {
            if (t.size() > 1) ans.push_back(t);
            return;
        }
        if (nums[u] >= last) {
            t.push_back(nums[u]);
            dfs(u + 1, nums[u], t, nums, ans);
            t.pop_back();
        }
        if (nums[u] != last) dfs(u + 1, last, t, nums, ans);
    }
};

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
func findSubsequences(nums []int) [][]int {
    var ans [][]int
    var dfs func(u, last int, t []int)
    dfs = func(u, last int, t []int) {
        if u == len(nums) {
            if len(t) > 1 {
                ans = append(ans, slices.Clone(t))
            }
            return
        }
        if nums[u] >= last {
            t = append(t, nums[u])
            dfs(u+1, nums[u], t)
            t = t[:len(t)-1]
        }
        if nums[u] != last {
            dfs(u+1, last, t)
        }
    }
    var t []int
    dfs(0, -1000, t)
    return ans
}

Comments