LeetCode Hot 100 螺旋矩阵

给你一个 m 行 n 列的矩阵 matrix ，请按照 顺时针螺旋顺序 ，返回矩阵中的所有元素。

示例 1：

输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
输出：[1,2,3,6,9,8,7,4,5]

示例 2：

输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
输出：[1,2,3,4,8,12,11,10,9,5,6,7]

提示：

• m == matrix.length
• n == matrix[i].length
• 1 <= m, n <= 10
• -100 <= matrix[i][j] <= 100

class Solution {
public:
    vector spiralOrder(vector>& matrix) {
        vector ans;

        int up = 0;
        int left =0;
        int down = matrix.size() -1;
        int right = matrix[0].size() -1;

        if(matrix.empty())
        {
            return ans;
        }

        while(true)
        {
            for(int i = left; i <= right; i ++)
            {
                ans.push_back(matrix[up][i]);
            }
            if(++up > down)
            {
                break;
            }

            for(int i = up; i <= down; i++)
            {
                ans.push_back(matrix[i][right]);
            }
            if(--right < left)
            {
                break;
            }

            for(int i = right; i >= left; i--)
            {
                ans.push_back(matrix[down][i]);

            }
            if(--down = up; i--)
            {
                ans.push_back(matrix[i][left]);
            }
            if(++left > right)
            {
                break;
            }
        }
        return ans;
    }
};