給定一個正整數 n，生成一個包含 1 到 n2 所有元素，且元素按順時針順序螺旋排列的正方形矩陣。

示例:

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

class Solution {
    public int[][] generateMatrix(int n) {
        int[][] arr = new int[n][n];
        int c = 1, j = 0;
        while (c <= n * n) {
        
            for (int i = j; i < n - j; i++)
                arr[j][i] 
 
= c++;
            for (int i = j + 1; i < n - j; i++)
                arr[i][n - j - 1] = c++;
            for (int i = n - j - 2; i >= j; i--)
                arr[n - j - 1][i] = c++;
            for (int i = n -j - 2; i > j; i--)
                arr[i][j] = c++;

            j++;
        }

        
 
return arr;
    }
}

力扣——螺旋矩陣 II