Java for LeetCode 059 Spiral Matrix II

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 ]
]

解题思路：

参考Java for LeetCode 054 Spiral Matrix，修改下代码即可，JAVA实现如下：

static public int[][] generateMatrix(int n) {
        if(n==0)
            return new int[0][0];
    	int[][] matrix=new int[n][n];
    	int num=0,left = 0, right = matrix[0].length - 1, up = 0, down = matrix.length - 1;
        while (left <= right && up <= down) {
            for (int i = left; i <= right&&up<=down; i++)
                matrix[up][i]=++num;
            up++;
            for (int i = up; i <= down&&left<=right; i++)
                matrix[i][right]=++num;
            right--;
            for (int i = right; i >= left&&up<=down; i--)
                matrix[down][i]=++num;
            down--;
            for (int i = down; i >= up&&left<=right; i--)
                matrix[i][left]=++num;
            left++;
        }
    	return matrix;
    }