Create a stack called numbers, which contains all numbers from 1 to 4 and initialise a variable k to be 1.

For the element k in a column, store the number in that element in a variable called value and call Search-Stack(numbers, value). If the function returns FALSE, then we should return FALSE as a number appears twice or not at all in the Stack. If the function returns the stack, increase the value of k by one.

If, after checking all elements in the column, SearchStack has not returned FALSE, we return TRUE.

Task 5: Complete the following function:

function CheckColumn(puzzle, j)

...

end function

This function will take the vector puzzle (as produced by MakeVector) as an input parameter and check that column j contains all numbers from 1 to 4: if it does contain all numbers from 1 to 4, it should return TRUE; otherwise, it should return FALSE. The procedure you should use is the one outlined above.

[4 marks]