spiral traversal of binary tree code example

Example: spiral order matrix traversal in C++

vector<int> Solution::spiralOrder(const vector<vector<int> > &A) {    int row_start = 0, row_end = A.size()-1, col_start = 0, col_end = A[0].size()-1;    vector<int> v;    while (row_start<=row_end  && col_start<=col_end)    {        //for row_start        for (int col = col_start; col<=col_end; col++)        {           v.push_back(A[row_start][col]);        }        row_start++;        //for col_end        for (int row = row_start; row<= row_end; row++)        {            v.push_back(A[row][col_end]);        }        col_end--;        //for row_end        for (int col = col_end; col>=col_start; col--)        {            v.push_back(A[row_end][col]);        }        row_end--;        //for col_start        for (int row = row_end; row>=row_start; row--)        {            v.push_back(A[row][col_start]);        }          col_start++;    }    return v;}XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX