




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.
"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 oneelement array? If so, then by using the recipe from the first paragraph you can find a method that prints all the permutations of a twoelement array. Applying the recipe to that method gives you a way to handle threeelement 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 N1, which you could do if you had a method for N2, 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@acmdotorg.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





