Initial data commit

Task/Magic-squares-of-singly-even-order/Java/magic-squares-of-singly-even-order.java

@@ -0,0 +1,85 @@
+public class MagicSquareSinglyEven {
+
+    public static void main(String[] args) {
+        int n = 6;
+        for (int[] row : magicSquareSinglyEven(n)) {
+            for (int x : row)
+                System.out.printf("%2s ", x);
+            System.out.println();
+        }
+        System.out.printf("\nMagic constant: %d ", (n * n + 1) * n / 2);
+    }
+
+    public static int[][] magicSquareOdd(final int n) {
+        if (n < 3 || n % 2 == 0)
+            throw new IllegalArgumentException("base must be odd and > 2");
+
+        int value = 0;
+        int gridSize = n * n;
+        int c = n / 2, r = 0;
+
+        int[][] result = new int[n][n];
+
+        while (++value <= gridSize) {
+            result[r][c] = value;
+            if (r == 0) {
+                if (c == n - 1) {
+                    r++;
+                } else {
+                    r = n - 1;
+                    c++;
+                }
+            } else if (c == n - 1) {
+                r--;
+                c = 0;
+            } else if (result[r - 1][c + 1] == 0) {
+                r--;
+                c++;
+            } else {
+                r++;
+            }
+        }
+        return result;
+    }
+
+    static int[][] magicSquareSinglyEven(final int n) {
+        if (n < 6 || (n - 2) % 4 != 0)
+            throw new IllegalArgumentException("base must be a positive "
+                    + "multiple of 4 plus 2");
+
+        int size = n * n;
+        int halfN = n / 2;
+        int subSquareSize = size / 4;
+
+        int[][] subSquare = magicSquareOdd(halfN);
+        int[] quadrantFactors = {0, 2, 3, 1};
+        int[][] result = new int[n][n];
+
+        for (int r = 0; r < n; r++) {
+            for (int c = 0; c < n; c++) {
+                int quadrant = (r / halfN) * 2 + (c / halfN);
+                result[r][c] = subSquare[r % halfN][c % halfN];
+                result[r][c] += quadrantFactors[quadrant] * subSquareSize;
+            }
+        }
+
+        int nColsLeft = halfN / 2;
+        int nColsRight = nColsLeft - 1;
+
+        for (int r = 0; r < halfN; r++)
+            for (int c = 0; c < n; c++) {
+                if (c < nColsLeft || c >= n - nColsRight
+                        || (c == nColsLeft && r == nColsLeft)) {
+
+                    if (c == 0 && r == nColsLeft)
+                        continue;
+
+                    int tmp = result[r][c];
+                    result[r][c] = result[r + halfN][c];
+                    result[r + halfN][c] = tmp;
+                }
+            }
+
+        return result;
+    }
+}