给定一个包含 m x n 个元素的矩阵（m 行, n 列），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:
[
 [ 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:
[
  [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]

Solution

官方题解思路：按层模拟

# @lc code=start
class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        if not matrix:
            return list()
        res = list()
        rows, columns = len(matrix), len(matrix[0])
        left, right, top, bottom = 0, columns - 1, 0, rows - 1
        while left<=right and top<=bottom:
            for column in range(left, right+1):
                res.append(matrix[top][column])
            for row in range(top+1, bottom+1):
                res.append(matrix[row][right])
                
            if left < right and top < bottom:
                for column in range(right-1, left, -1):
                    res.append(matrix[bottom][column])
                for row in range(bottom, top, -1):
                    res.append(matrix[row][left])
            
            left, right, top, bottom = left+1, right-1, top+1, bottom-1
        return res
# @lc code=end

c++

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>> &matrix) {
        if (matrix.empty()) return {};

        vector<int> res;
        int rows = matrix.size(), cols = matrix[0].size();
        int left = 0, right = cols - 1, top = 0, bottom = raws-1;

        while (left <= right && top <= bottom) {
            for (int col = left; col < right; ++col) {
                res.push_back(matrix[top][col]);
            }
            for (int row = top+1; row < bottom; ++row) {
                res.push_back(matrix[row][right]);
            }
            if (left < right && top < bottom) {
                for (int col = right-1; col > left; --col) {
                    res.push_back(matrix[bottom][col]);
                }
                for (int row = bottom; row > top; --row) {
                    res.push_back(matrix[row][left]);
                }
            }
            ++left, --right;
            ++top, --bottom;
        }
        return res;
    }
};