Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,

Given n = 3,

You should return the following matrix:

[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ]]

思路：与上一篇类似。仅仅要不越界就ok

public class Solution {	public int[][] generateMatrix(int n) {	    if (n == 0)			return new int[0][0];		int[][] matrix = new int[n][n];		int x1 = 0;		int y1 = 0;		int x2 = matrix.length - 1;		int y2 = matrix[0].length - 1;		int i = 0, j = 1;		while (x1 <= x2 && y1 <= y2) {			// up row			for (i = y1; i <= y2; ++i, j++)				matrix[x1][i] = j;			// right column			for (i = x1 + 1; i <= x2; ++i, j++)				matrix[i][y2] = j;			// bottom row			for (i = y2 - 1; x2 != x1 && i >= y1; --i, j++)				matrix[x2][i] = j;			// left column			for (i = x2 - 1; y1 != y2 && i > x1; --i, j++)				matrix[i][y1] = j;			x1++;			y1++;			x2--;			y2--;		}		return matrix;	}}

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