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How to Shuffle elements of an Array without repeating the same sequence?

For example if i have the following array:
int vector[] = {"a", "b", "c"};
i want to get 3 different sequences without repeats. For example i dont want to get
{"b", "c", "a"} //duplicated {"b", "c", "a"} //duplicated {"a", "b", "c"}

I'd give a look at next_permutation.

@JohanSolo But it will give me a nodistribuited result

@Eduardo12l I'm not sure to understand what you mean....

@JohanSolo If you run this algorithm you could notice what is the problem of next_permutation
#include <iostream> #include <algorithm> #include <string> #include <cstdlib> using namespace std; int main() { string vector[] = {"a", "b", "c", "d", "e", "f", "g", "h"}; for (int c = 0; c < 20; c++) { std::next_permutation(begin(vector), end(vector)); for (int i = 0; i < 8; i++) { cout << vector[i] << " "; } cout << endl; cout << "" << endl; } system("pause"); }

@Eduardo12l I'm sorry but I don't. I know what a permutation looks like (moreover the page I gave you shows an example). I'll try once I have a compiler but I don't expect to be surprised.
In your code the hardcoded 20 is clearly wrong: there are much more permutations for a set of 8 elements (8! is not 20), but that's a detail.
Edit: in your first post you said you want the 3 permutations of a set with 3 elements. This is wrong again, there are 6 permutations. You should probably define better what you want so that you can be helped.

OK, now I'm at work and I have several compilers at hand. The result is
pretty close toexactly what I expected:a b c d e f h g a b c d e g f h a b c d e g h f a b c d e h f g a b c d e h g f a b c d f e g h a b c d f e h g a b c d f g e h a b c d f g h e a b c d f h e g a b c d f h g e a b c d g e f h a b c d g e h f a b c d g f e h a b c d g f h e a b c d g h e f a b c d g h f e a b c d h e f g a b c d h e g f a b c d h f e g
What output did you expect?

I had some time in my break..
I think the OP is looking for something like this?#include <QCoreApplication> #include <QVector> #include <QDebug> QVector<QChar> vector {'a','b','c','d','e','f'}; uint64_t factorial (uint64_t i){ uint64_t fac(1); for(uint64_t j = 1; j <= i; j++) fac = fac*i; return fac; } QList<QVector<QChar>> getAllPermutations(){ QList<QVector<QChar>> list; uint64_t max = factorial(vector.size()); for(uint64_t i = 0; i< max; i++){ std::next_permutation(vector.begin(), vector.end()); list.append(vector); } return list; } QList<QVector<QChar>> selectSome(int cnt, QList<QVector<QChar>> pool){ QList<QVector<QChar>> list; for(int i = 0; i < cnt; i++){ int index = rand()%pool.size(); list.append(pool.at(index)); } return list; } int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); QList<QVector<QChar>> pool = getAllPermutations(); QList<QVector<QChar>> selection = selectSome(3,pool); for(auto item : selection) qDebug() << item; return a.exec(); }

@J.Hilk said in How to Shuffle elements of an Array without repeating the same sequence?:
I had some time in my break..
I think the OP is looking for something like this?Makes sense, all we were missing was the actual requirement "I want some permutations without repetitions".

@JohanSolo Actually, now that you say it,
theres a chance for repetitions inselectSome
QList<QVector<QChar>> selectSome(int cnt, QList<QVector<QChar>> pool){ QList<QVector<QChar>> list; QVector<int> usedIndex; int i(0); while(i < cnt && usedIndex.size() < pool.size(){ int index = rand()%pool.size(); if(!usedIndex.contains(index)){ usedIndex.append(index); list.append(pool.at(index)); } } return list; }
this should be better, still not perfect, but at least no repetitions, possible infinite loop when pool.size() > sizeOf(int)? Gets very slow for big
cnt
!