Motivation: In many problems, we need to create combinations with the function nchoosek. In some cases, however, choices are limited in particular fields. This problem is an exercise based on this issue.

Problem statement: Given a vector v, create a combination matrix where an element on i-th column can not exceed v(i). All values of input vector will be of single digit.

Example:

v = [1 3 2];
Output =[
     1     1     1
     1     1     2
     1     2     1
     1     2     2
     1     3     1
     1     3     2 ];