打印螺旋矩阵.java

package com.qidu.lin;

public class PrinterNumbers
{
	/**
	 * 打印螺旋矩阵
0  31  30  29  28  27  26  25  24 
1  32  55  54  53  52  51  50  23 
2  33  56  71  70  69  68  49  22 
3  34  57  72  79  78  67  48  21 
4  35  58  73  80  77  66  47  20 
5  36  59  74  75  76  65  46  19 
6  37  60  61  62  63  64  45  18 
7  38  39  40  41  42  43  44  17 
8   9  10  11  12  13  14  15  16 
	 */
	public static void main(String a[])
	{
		final int N = 9;
		for (int row = 0; row < N; row++)
		{
			for (int col = 0; col < N; col++)
			{
				// 别问我，两年后再看， 我也不知道这个公式是怎么推出来的。
				int round = Math.min(Math.min(row, col), Math.min(N - 1 - row, N - 1 - col));
				int total = Math.max(1,  4 * N - 4 - 8 * round);
				int num = (4 * round * (N - round)) + ((total + (row < col ? -1 : 1) * (row + col - 2 * round)) % total);

				System.out.print(String.format("%3d", num));
				System.out.print(" ");
			}
			System.out.print("\n");
		}
	}
}

迷一样啊，老哥