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