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465. Find all subsets of size K from a given number N (1 to N)
Objective: Given two integers N and K, Write an algorithm to find subsets of size K from the numbers 1 to N.
Example:
N = 5 K = 3 Output: [1, 2, 3] [1, 2, 4] [1, 2, 5] [1, 3, 4] [1, 3, 5] [1, 4, 5] [2, 3, 4] [2, 3, 5] [2, 4, 5] [3, 4, 5] N = 6 K = 5 Output: [1, 2, 3, 4, 5] [1, 2, 3, 4, 6] [1, 2, 3, 5, 6] [1, 2, 4, 5, 6] [1, 3, 4, 5, 6] [2, 3, 4, 5, 6]
Approach: Use Recursion
 Given N and subset size K.
 Start with startNumber = 0, combinationList=null
 Iterate through i = startNumber to N.
 Put i to combinationList.
 Make a recursive call with startNumber=i+1, K=K1 and (to process next elements) and combinationList.
 In tail recursion, backtrack and remove i from the combinationList to find more solutions
 Base case: if K=0, Print combinationList.
Output:
Given Number: 6, subset size K: 5 [1, 2, 3, 4, 5] [1, 2, 3, 4, 6] [1, 2, 3, 5, 6] [1, 2, 4, 5, 6] [1, 3, 4, 5, 6] [2, 3, 4, 5, 6]