118. Print All Combinations of subset of size K from Given Array

Objective: Given an array of integers of size N, print all the subsets of size k. (k<=N)

Example:

Generate all subsets of a fixed size k of a given set [1,2,3...n]. e.g, if n=5 and k=3, the output will look like

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

Approach:

Create an boolean array of the same size as the given array.
Now for every integer we have two options, whether to select it or ignore it.
Now if we select it, we will put TRUE in the boolean array at the corresponding index or if we ignore it, put FALSE at that index.
We will start with currentLength =0 and do the recursive calls for both the options mentioned in the previous step.
If we select an integer to print, make currentLength +1 and if we ignore, dont change currentLength.
Another important factor is from which index you will start making the subset of size k. Initialize start = 0, and with every recursive call, make start + 1 ( for both the scenarios mentioned in the steps above).
Print the elements when currentLength = k.

Note: Click on the image to enlarge it.

Output: