Your overall approach is sound. I’m pretty sure the problem lies with your make_canonical function. You can try printing out the hands with num_cards set to 3 or 4 and look for equivalencies that you’ve missed. I found one, but there may be more: # The inputs are equivalent and should return the same value … Read more
This function, perm(xs), returns all the permutations of a given array: function perm(xs) { let ret = []; for (let i = 0; i < xs.length; i = i + 1) { let rest = perm(xs.slice(0, i).concat(xs.slice(i + 1))); if(!rest.length) { ret.push([xs[i]]) } else { for(let j = 0; j < rest.length; j = j … Read more
I’m very slightly skeptical that there is a solution. Your problem seems to be very close to one posed several years ago in the mathematical literature, with a summary given here (“The Duplicate Detection Problem”, S. Kamal Abdali, 2003) that uses cycle-detection — the idea being the following: If there is a duplicate, there exists … Read more
if n is not far from r then using the recursive definition of combination is probably better, since xC0 == 1 you will only have a few iterations: The relevant recursive definition here is: nCr = (n-1)C(r-1) * n/r This can be nicely computed using tail recursion with the following list: [(n – r, 0), … Read more
Let’s write a function that returns all permutations of a string as an array. As you don’t want any global variables, returning the permutations is crucial. function permut(string) { if (string.length < 2) return string; // This is our break condition var permutations = []; // This array will hold our permutations for (var i … Read more
You should use the fact that when you want all permutations of N numbers there are N! possibilities. Therefore each number x from 1..N! encodes such a permutation. Here is a sample that iteratively prints out all permutations of a sting. private static void printPermutationsIterative(String string){ int [] factorials = new int[string.length()+1]; factorials[0] = 1; … Read more
Here is a non-recursive algorithm in C++ from the Wikipedia entry for unordered generation of permutations. For the string s of length n, for any k from 0 to n! – 1 inclusive, the following modifies s to provide a unique permutation (that is, different from those generated for any other k value on that … Read more