So i am trying to find a solution to no repeats , i read and found if there are no repeat character then the formulae is permutation of n things taken n at a time, and the formulae is -
n!/n! - r! , so if i were to take abcdefa at a time , it would mean 7!/7! - 2! but the result does not match FCC results …
Or is it 7!/2! where 2 is the number of times a is repeated ?
Or do i need to find all permutation like 7! = 5040 and subtract it with something
Then i looked for solution and came across stackoverflow and youtube videos but got even more confused , can any one who has done this kindly explain what i need to do …Thanks