螺旋矩阵II

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

Example:

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

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/spiral-matrix-ii
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

建立top,bottom,left,right四个边界，创建n*n二维数组并逆时针赋值，当到达边界时，上、左边界自增，右、下边界自减，当top>bottom或left>right时，结束循环。代码如下：

    public int[][] generateMatrix(int n) {

        int[][] res = new int[n][n];

        int top = 0;

        int bottom = n-1;

        int left = 0;

        int right = n-1;

        int target = 1;

        //看了一下题解，有的大佬把判断循环是否结束的语句设置为target<=n*n

        while(top <= bottom || left <= right)

        {

            //从左往右

            for(int i = left; i <= right; i++)

            {

                res[top][i] = target++;

            }

            top++;

            //从上往下

            for(int i = top; i <= bottom; i++)

            {

                res[i][right] = target++;

            }

            right--;

            //从右往左

            for(int i = right; i >= left; i--)

            {

                res[bottom][i] = target++;

            }

            bottom--;

            //从下往上

            for(int i = bottom; i >= top; i--)

            {

                res[i][left] = target++;

            }

            left++;

        }

        return res;

    }

巴特西

螺旋矩阵II

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