[剑指offer] 19. 顺时针打印矩阵

class Solution
{
public:
  vector<int> printMatrix(vector<vector<int>> matrix)
  {
    int bottom = matrix.size() - 1;
    int right = matrix[0].size() - 1;
    vector<int> res;

    if (bottom < 0 || right < 0)
      return res;

    int top = 0, left = 0;
    while (left <= right && top <= bottom)
    {
      // 左到右
      for (int i = left; i <= right; i++)
        res.push_back(matrix[top][i]);

      // 上到下
      for (int j = top + 1; j <= bottom; j++)
        res.push_back(matrix[j][right]);
      // 右到左
      if (top != bottom)
        for (int k = right - 1; k >= left; k--)
          res.push_back(matrix[bottom][k]);
      // 下到上
      if (left != right)
        for (int l = bottom - 1; l > top; l--)
          res.push_back(matrix[l][left]);
      left++, top++, right--, bottom--;
    }
    return res;
  }
};