Random Latin squares: Difference between revisions
→{{header|C sharp|C#}}
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* [http://oeis.org/A002860 OEIS A002860]
<br>
=={{header|C++}}==
{{trans|Java}}
<lang cpp>#include <algorithm>
#include <chrono>
#include <iostream>
#include <random>
#include <vector>
template <typename T>
std::ostream &operator<<(std::ostream &os, const std::vector<T> &v) {
auto it = v.cbegin();
auto end = v.cend();
os << '[';
if (it != end) {
os << *it;
it = std::next(it);
}
while (it != end) {
os << ", ";
os << *it;
it = std::next(it);
}
return os << ']';
}
void printSquare(const std::vector<std::vector<int>> &latin) {
for (auto &row : latin) {
std::cout << row << '\n';
}
std::cout << '\n';
}
void latinSquare(int n) {
if (n <= 0) {
std::cout << "[]\n";
return;
}
// obtain a time-based seed:
unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
auto g = std::default_random_engine(seed);
std::vector<std::vector<int>> latin;
for (int i = 0; i < n; ++i) {
std::vector<int> inner;
for (int j = 0; j < n; ++j) {
inner.push_back(j);
}
latin.push_back(inner);
}
// first row
std::shuffle(latin[0].begin(), latin[0].end(), g);
// middle row(s)
for (int i = 1; i < n - 1; ++i) {
bool shuffled = false;
while (!shuffled) {
std::shuffle(latin[i].begin(), latin[i].end(), g);
for (int k = 0; k < i; ++k) {
for (int j = 0; j < n; ++j) {
if (latin[k][j] == latin[i][j]) {
goto shuffling;
}
}
}
shuffled = true;
shuffling: {}
}
}
// last row
for (int j = 0; j < n; ++j) {
std::vector<bool> used(n, false);
for (int i = 0; i < n - 1; ++i) {
used[latin[i][j]] = true;
}
for (int k = 0; k < n; ++k) {
if (!used[k]) {
latin[n - 1][j] = k;
break;
}
}
}
printSquare(latin);
}
int main() {
latinSquare(5);
latinSquare(5);
latinSquare(10);
return 0;
}</lang>
{{out}}
<pre>[4, 3, 1, 2, 0]
[1, 0, 3, 4, 2]
[3, 2, 0, 1, 4]
[2, 1, 4, 0, 3]
[0, 4, 2, 3, 1]
[2, 4, 0, 3, 1]
[0, 3, 4, 1, 2]
[3, 0, 1, 2, 4]
[1, 2, 3, 4, 0]
[4, 1, 2, 0, 3]
[9, 3, 5, 0, 8, 2, 7, 1, 6, 4]
[0, 9, 4, 6, 1, 8, 5, 3, 7, 2]
[4, 1, 9, 7, 3, 5, 2, 0, 8, 6]
[2, 6, 8, 3, 4, 0, 9, 7, 1, 5]
[6, 5, 3, 4, 7, 9, 1, 8, 2, 0]
[1, 8, 6, 5, 2, 4, 0, 9, 3, 7]
[7, 2, 0, 8, 9, 1, 4, 6, 5, 3]
[3, 0, 7, 1, 5, 6, 8, 2, 4, 9]
[8, 4, 2, 9, 6, 7, 3, 5, 0, 1]
[5, 7, 1, 2, 0, 3, 6, 4, 9, 8]</pre>
=={{header|C sharp|C#}}==
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