C Programming Language :: to print permutations...


	to print permutations... Suppose we are having 3 variables...a,b,c And we want to print the permutations of these variables...Such as...abc,acb,bca...all 6 of them... But we are not supposed to do it mannually... I want to know that formula by which this can be possible... Then that program will be ok for nnumber of variables.... Can anyone help me for that? "Shraddha" wrote: > Suppose we are having 3 variables...a,b,c > And we want to print the permutations of these variables...Such > as...abc,acb,bca...all 6 of them... > But we are not supposed to do it mannually... > I want to know that formula by which this can be possible... > Then that program will be ok for nnumber of variables.... > Can anyone help me for that? This might help http://en.wikipedia.org/wiki/Permutations#Permutations_in_computing It seems to have some "Pascalish" looking source code. Because of the difficulties of handling templates, I would expect the source code used by next_permutation ( or whatever) is in the \include\ directory of your compiler. I never actually looked, though. On 5 26 , 9 13 , Shraddha <shraddhajosh@gmail.com> wrote: > Suppose we are having 3 variables...a,b,c > And we want to print the permutations of these variables...Such > as...abc,acb,bca...all 6 of them... > But we are not supposed to do it mannually... > I want to know that formula by which this can be possible... > Then that program will be ok for nnumber of variables.... > Can anyone help me for that? I think it's a algorithm problem. You should study the combination mathematics. There is the algorithm for generating permutations in this course. - Hide quoted text - "osmium" writes: > "Shraddha" wrote: >> Suppose we are having 3 variables...a,b,c >> And we want to print the permutations of these variables...Such >> as...abc,acb,bca...all 6 of them... >> But we are not supposed to do it mannually... >> I want to know that formula by which this can be possible... >> Then that program will be ok for nnumber of variables.... >> Can anyone help me for that? > This might help > http://en.wikipedia.org/wiki/Permutations#Permutations_in_computing > It seems to have some "Pascalish" looking source code. > Because of the difficulties of handling templates, I would expect the > source code used by next_permutation ( or whatever) is in the \include\ > directory of your compiler. I never actually looked, though. The OP is flitting around amongst newsgroups, thus the C++ answer in a C newsgroup. Sorry. The answer is formed with respect to a question and answer the OP got a few days ago. Shraddha wrote: > Suppose we are having 3 variables...a,b,c > And we want to print the permutations of these variables...Such > as...abc,acb,bca...all 6 of them... > But we are not supposed to do it mannually... > I want to know that formula by which this can be possible... > Then that program will be ok for nnumber of variables.... > Can anyone help me for that? Imagine that you had a function that would print all the permutations of an array of N variables. Can you think of a way to use that function to print all the permutations of an array of N+1 variables? Second question: Suppose N is equal to one. Can you think of a way to print all the permutations of a one-element array? If so, then by using the recipe from the first paragraph you can find a method that prints all the permutations of a two-element array. Applying the recipe to that method gives you a way to handle three-element arrays, then four, then five, ... A convenient way to express this in C is to turn the problem around. The recipe tells you how to permute N elements if only you had a method for permuting N-1, which you could do if you had a method for N-2, and so on. Eventually you get down to "If only I had a method for permuting one element," which you'll need to solve on your own. If that's not enough of a hint, you haven't been paying enough attention in class. Ask your teacher for remedial help. -- Eric sosman esos@acm-dot-org.invalid "Shraddha" <shraddhajosh@gmail.com> wrote in message news:1180185229.464276.33190@z28g2000prd.googlegroups.com... > Suppose we are having 3 variables...a,b,c > And we want to print the permutations of these variables...Such > as...abc,acb,bca...all 6 of them... > But we are not supposed to do it mannually... > I want to know that formula by which this can be possible... > Then that program will be ok for nnumber of variables.... > Can anyone help me for that? You've got N! permutations of a string. So the manual approach breaks down at about 6, the computer approach at something like N=15. As the said, Eric Sosman bascially you need to take each element in turn, then permute the remainder. So code looks something like this /* give user a nice wrapper, permute a string to an output / void permute(char str, FILE fpout) { char buff[20]; / you will never need more than 20 characters unless you have a really super duper computer / / start with an empty prefix / strcpy(buff, ""); permuter(buff, str, fpout); } / real function is recursive. We print a prefix / static void permuter(char prefix, char str, FILE fp) { /* check for strings of length 1, print them (with prefix), and terminate / / take each element of the string, add it to the prefix, then call permuter() on the remaining elements */ } -- Free games and programming goodies. http://www.personal.leeds.ac.uk/~bgy1mm