leetcode - Spiral Matrix

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

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

You should return [1,2,3,6,9,8,7,4,5].

class Solution {
public:
    std::vector
  
    spiralOrder(std::vector
   
     > &matrix) { std::vector
    
      res; if(matrix.size() == 0) return res; int rowBgn = 0, rowEnd = matrix.size() - 1,colBgn = 0,colEnd = matrix[0].size() - 1; while (rowBgn <= rowEnd && colBgn <= colEnd) { //right for(int i = colBgn; i <= colEnd; i++) { res.push_back(matrix[rowBgn][i]); } rowBgn++; //Down for(int i = rowBgn; i <= rowEnd; i++) { res.push_back(matrix[i][colEnd]); } colEnd--; //left if (rowBgn <= rowEnd) { for(int i = colEnd; i >= colBgn; i--) { res.push_back(matrix[rowEnd][i]); } } rowEnd--; //up if (colBgn <= colEnd) { for(int i = rowEnd; i >= rowBgn; i--) { res.push_back(matrix[i][colBgn]); } } colBgn++; } return res; } };