LeetCode 54. 螺旋矩阵

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]

 

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        if (matrix.empty() || matrix[0].empty())
            return {};

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

        int i = 0, j = 0;
        while (true)
        {
            if (j > right)
                break;
            while (j <= right)
                res.push_back(matrix[i][j++]);
            top++;
            i++;
            j = right;

            if (i > bottom)
                break;
            while (i <= bottom)
                res.push_back(matrix[i++][j]);
            right--;
            j--;
            i = bottom;

            if (j < left)
                break;
            while (j >= left)
                res.push_back(matrix[i][j--]);
            bottom--;
            i--;
            j = left;

            if (i < top)
                break;
            while (i >= top)
                res.push_back(matrix[i--][j]);
            left++;
            j++;
            i = top;
        }

        return res;
    }
};