Simple factorial and matrix question

  • Thread starter Thread starter arpace
  • Start date Start date
  • Tags Tags
    Factorial Matrix
AI Thread Summary
To ensure that numbers from 1 to n are used without repetition in n slots, multiplying the values in each slot and comparing the product to n! is a valid approach. This method confirms that each number appears exactly once, similar to a Sudoku rule for rows. For validating the entire grid, using (n!)^n can help check all combinations. The concept of permutations is relevant here, as there are n! ways to arrange the numbers uniquely. Understanding these principles can simplify the validation process for such arrangements.
arpace
Messages
9
Reaction score
0
if I have n slots [1,2,3,4,5,...n] where I must use numbers from 1 through n, and I have to ensure that none of them were reused...

the way I figure to make sure that none of the numbers are reused is to multiply the values in each slot and compare them against n!

e.g. [1,2,3,4,5] would be correct, but [1,4,6,3,2] or [5,5,2,1,3]

kind of like sudoku's rule for a row but not quite
e.g. if I had n=6
[[1,2,3,4,5,6],
[6,1,2,3,4,5],
[5,6,1,2,3,4],
[4,5,6,1,2,3],
[3,4,5,6,1,2]]
that would be correct

Am I right in assuming that that n! would be useful for looping through the rows to see if they are correct? and then (n!)^(n) would be a way to validate the entire grid?

is this a rule I just don't know? is there a rule that is easier?
 
Last edited:
Mathematics news on Phys.org
arpace said:
if I have n slots [1,2,3,4,5,...n] where I must use numbers from 1 through n, and I have to ensure that none of them were reused...

the way I figure to make sure that none of the numbers are reused is to multiply the values in each slot and compare them against n!

e.g. [1,2,3,4,5] would be correct, but [1,4,6,3,2] or [5,5,2,1,3]

kind of like sudoku's rule for a row but not quite
e.g. if I had n=6
[[1,2,3,4,5,6],
[6,1,2,3,4,5],
[5,6,1,2,3,4],
[4,5,6,1,2,3],
[3,4,5,6,1,2]]
that would be correct

Am I right in assuming that that n! would be useful for looping through the rows to see if they are correct? and then (n!)^(n) would be a way to validate the entire grid?

is this a rule I just don't know? is there a rule that is easier?



Google "permutations", and yes: there are n! different ways to order in an array the numbers 1,2,...,n in such a way that each

appears exactly once.

DonAntonio
 
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Back
Top