Combinations LeetCode Programming Solutions | LeetCode Problem Solutions in C++, Java, & Python [💯Correct]

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Hello Programmers/Coders, Today we are going to share solutions to the Programming problems of LeetCode Solutions in C++, Java, & Python. At Each Problem with Successful submission with all Test Cases Passed, you will get a score or marks and LeetCode Coins. And after solving maximum problems, you will be getting stars. This will highlight your profile to the recruiters.

In this post, you will find the solution for the Combinations in C++, Java & Python-LeetCode problem. We are providing the correct and tested solutions to coding problems present on LeetCode. If you are not able to solve any problem, then you can take help from our Blog/website.

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LeetCode is one of the most well-known online judge platforms to help you enhance your skills, expand your knowledge and prepare for technical interviews. 

LeetCode is for software engineers who are looking to practice technical questions and advance their skills. Mastering the questions in each level on LeetCode is a good way to prepare for technical interviews and keep your skills sharp. They also have a repository of solutions with the reasoning behind each step.

LeetCode has over 1,900 questions for you to practice, covering many different programming concepts. Every coding problem has a classification of either Easy, Medium, or Hard.

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• Mathematics/Basic Logical Based Questions
• Arrays
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• Dynamic Programming
• Stack & Queue
• Trees & Graphs
• Greedy Algorithms
• Breadth-First Search
• Depth-First Search
• Sorting & Searching
• BST (Binary Search Tree)
• Database
• Linked List
• Recursion, etc.

Leetcode has a huge number of test cases and questions from interviews too like Google, Amazon, Microsoft, Facebook, Adobe, Oracle, Linkedin, Goldman Sachs, etc. LeetCode helps you in getting a job in Top MNCs. To crack FAANG Companies, LeetCode problems can help you in building your logic.

Link for the Problem – Combinations– LeetCode Problem

Combinations– LeetCode Problem

Problem:

Given two integers n and k, return all possible combinations of k numbers out of the range [1, n].

You may return the answer in any order.

Example 1:

Input: n = 4, k = 2
Output:
[
  [2,4],
  [3,4],
  [2,3],
  [1,2],
  [1,3],
  [1,4],
]

Example 2:

Input: n = 1, k = 1
Output: [[1]]

Constraints:

• 1 <= n <= 20
• 1 <= k <= n

Combinations– LeetCode Solutions

Combinations Solution in C++:

class Solution {
 public:
  vector<vector<int>> combine(int n, int k) {
    vector<vector<int>> ans;

    dfs(n, k, 1, {}, ans);

    return ans;
  }

 private:
  void dfs(int n, int k, int s, vector<int>&& path, vector<vector<int>>& ans) {
    if (k == 0) {
      ans.push_back(path);
      return;
    }

    for (int i = s; i <= n; ++i) {
      path.push_back(i);
      dfs(n, k - 1, i + 1, move(path), ans);
      path.pop_back();
    }
  }
};

Combinations in Java:

class Solution {
  public List<List<Integer>> combine(int n, int k) {
    List<List<Integer>> ans = new ArrayList<>();

    dfs(n, k, 1, new ArrayList<>(), ans);

    return ans;
  }

  private void dfs(int n, int k, int s, List<Integer> path, List<List<Integer>> ans) {
    if (k == 0) {
      ans.add(new ArrayList<>(path));
      return;
    }

    for (int i = s; i <= n; ++i) {
      path.add(i);
      dfs(n, k - 1, i + 1, path, ans);
      path.remove(path.size() - 1);
    }
  }
}

Combinations in Python:

class Solution:
  def combine(self, n: int, k: int) -> List[List[int]]:
    ans = []

    def dfs(n: int, k: int, s: int, path: List[int]) -> None:
      if k == 0:
        ans.append(path)
        return

      for i in range(s, n + 1):
        dfs(n, k - 1, i + 1, path + [i])

    dfs(n, k, 1, [])

    return ans