Problem 45303. Combinatorics - 01

• Input=[x,n]
• where x is an array of numbers(or strings) and n is a +ve number.

for example, x=[1,2] and n=6.

The output will be a matrix containing all the possible permutations of the vector x having n elements(no of columns=n). besides that -

• each row should contain equal number of occurance of the elements of x. (3 ones, 3 twos)
• no initial segment can have more 2's than 1's. e.g. [2 2 1 2 1 1] - is invalid.since there are more 2's in the 1st appearance than 1's.

• y=[

     1     1     1     2     2     2
     1     1     2     1     2     2
     1     1     2     2     1     2
     1     2     1     1     2     2
     1     2     1     2     1     2
     1     2     1     2     2     1
     2     1     1     1     2     2
     2     1     1     2     1     2
     2     1     1     2     2     1
     2     1     2     1     1     2
     2     1     2     1     2     1
     2     1     2     2     1     1
     2     2     1     1     1     2
     2     2     1     1     2     1
     2     2     2     1     1     1]