0 votes 0 votes explain me briefly what is valid stack stack permutations ? Magma asked Nov 14, 2018 Magma 919 views answer comment Share Follow See all 11 Comments See all 11 11 Comments reply Show 8 previous comments Somoshree Datta 5 commented Nov 14, 2018 reply Follow Share Magma u will pick each of the 6 combinations one by one and see whether it is valid or not provided the input comes in the sequence 1,2,3..if it is valid then it becomes a valid stack permutation. I guess this takes much lesser amount of time rather than trying to derive the equation given :3 0 votes 0 votes Sayan Bose commented Nov 14, 2018 reply Follow Share Magma Deriving a generic formula for valid stack permutations isn't easy and neither is it explained in any of the standard books. I remember this formula from the various applications of Catalan number I read here : https://www.geeksforgeeks.org/applications-of-catalan-numbers/. I recommend going through this , it will be of use for solving various other problems too in which Catalan number has been applied directly 0 votes 0 votes Manas Mishra commented Nov 14, 2018 reply Follow Share @somoshree supppose in exam if asked in NAT that find no of invalid stack permutation for inputs , then it will obvioulsy take a long time to deive using hit and trial method 0 votes 0 votes Please log in or register to add a comment.
