Data commit

Task/Random-Latin-squares/C-sharp/random-latin-squares.cs

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+using System;
+using System.Collections.Generic;
+
+namespace RandomLatinSquares {
+    using Matrix = List<List<int>>;
+
+    // Taken from https://stackoverflow.com/a/1262619
+    static class Helper {
+        private static readonly Random rng = new Random();
+
+        public static void Shuffle<T>(this IList<T> list) {
+            int n = list.Count;
+            while (n > 1) {
+                n--;
+                int k = rng.Next(n + 1);
+                T value = list[k];
+                list[k] = list[n];
+                list[n] = value;
+            }
+        }
+    }
+
+    class Program {
+        static void PrintSquare(Matrix latin) {
+            foreach (var row in latin) {
+                Console.Write('[');
+
+                var it = row.GetEnumerator();
+                if (it.MoveNext()) {
+                    Console.Write(it.Current);
+                }
+                while (it.MoveNext()) {
+                    Console.Write(", ");
+                    Console.Write(it.Current);
+                }
+
+                Console.WriteLine(']');
+            }
+            Console.WriteLine();
+        }
+
+        static void LatinSquare(int n) {
+            if (n <= 0) {
+                Console.WriteLine("[]");
+                return;
+            }
+
+            var latin = new Matrix();
+            for (int i = 0; i < n; i++) {
+                List<int> temp = new List<int>();
+                for (int j = 0; j < n; j++) {
+                    temp.Add(j);
+                }
+                latin.Add(temp);
+            }
+            // first row
+            latin[0].Shuffle();
+
+            // middle row(s)
+            for (int i = 1; i < n - 1; i++) {
+                bool shuffled = false;
+
+                while (!shuffled) {
+                    latin[i].Shuffle();
+                    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++) {
+                List<bool> used = new List<bool>();
+                for (int i = 0; i < n; i++) {
+                    used.Add(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);
+        }
+
+        static void Main() {
+            LatinSquare(5);
+            LatinSquare(5);
+            LatinSquare(10); // for good measure
+        }
+    }
+}