Combinations LeetCode Solution

Here, We see Combinations LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

List of all LeetCode Solution

Problem Statement

Given two integers `n` and `k`, return all possible combinations of `k` numbers are chosen from the range `[1, n]`.

You may return the answer in any order.

```Example 1:

Input: n = 4, k = 2
Output: [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]
Explanation: There are 4 choose 2 = 6 total combinations.
Note that combinations are unordered, i.e., [1,2] and [2,1] are considered to be the same combination.

Example 2:

Input: n = 1, k = 1
Output: [[1]]
Explanation: There is 1 choose 1 = 1 total combination.
```

Combinations Leetcode Solution C++

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

help(1, temp, ans, n, k);
return ans;
}

void help(int num, vector<int> &temp, vector<vector<int>> &ans, int n, int k){
if(temp.size() == k){
ans.push_back(temp);
return;
}
for(int i=num; i<=n; i++){
temp.push_back(i);
help(i+1, temp, ans, n, k);
temp.pop_back();
}
}
};```Code language: JavaScript (javascript)```

Combinations Leetcode Solution Java

``````class Solution {
public List<List<Integer>> combine(int n, int k) {
List<List<Integer>> result = new ArrayList<List<Integer>>();
if (k > n || k < 0) {
return result;
}
if (k == 0) {
return result;
}
result = combine(n - 1, k - 1);
for (List<Integer> list : result) {
}
return result;
}
}```Code language: PHP (php)```

Combinations Leetcode Solution JavaScript

``````var combine = function(n, k) {
if (n == 1 && k == 1) return [[1]];
let out = [];
const dfs = (currentSolution, startNumber, out) => {
if (currentSolution.length == k) out.push(Array.from(currentSolution));
for (let i = startNumber; i <= n; i++) {
currentSolution.push(i);
dfs(currentSolution, i + 1, out);
currentSolution.pop();
}
}
dfs([], 1, out);
return out;
};```Code language: JavaScript (javascript)```

Combinations Leetcode Solution Python

``````class Solution(object):
def combine(self, n, k):
if k == 0:
return [[]]
return [pre + [i] for i in range(k, n+1) for pre in self.combine(i-1, k-1)]``````
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