43. Combinations

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Input: n = 4, k = 2

Output: [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]

Explanation: All possible combinations of 2 numbers chosen from the range [1, 4].

Input: n = 1, k = 1

Output: [[1]]

Explanation: The only possible combination of 1 number chosen from the range [1, 1].

Time Complexity

O(C(n,k))

Space Complexity

O(k)