<p>You start at the cell <code>(rStart, cStart)</code> of an <code>rows x cols</code> grid facing east. The northwest corner is at the first row and column in the grid, and the southeast corner is at the last row and column.</p>

<p>You will walk in a clockwise spiral shape to visit every position in this grid. Whenever you move outside the grid&#39;s boundary, we continue our walk outside the grid (but may return to the grid boundary later.). Eventually, we reach all <code>rows * cols</code> spaces of the grid.</p>

<p>Return <em>an array of coordinates representing the positions of the grid in the order you visited them</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://s3-lc-upload.s3.amazonaws.com/uploads/2018/08/24/example_1.png" style="width: 174px; height: 99px;" />
<pre>
<strong>Input:</strong> rows = 1, cols = 4, rStart = 0, cStart = 0
<strong>Output:</strong> [[0,0],[0,1],[0,2],[0,3]]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://s3-lc-upload.s3.amazonaws.com/uploads/2018/08/24/example_2.png" style="width: 202px; height: 142px;" />
<pre>
<strong>Input:</strong> rows = 5, cols = 6, rStart = 1, cStart = 4
<strong>Output:</strong> [[1,4],[1,5],[2,5],[2,4],[2,3],[1,3],[0,3],[0,4],[0,5],[3,5],[3,4],[3,3],[3,2],[2,2],[1,2],[0,2],[4,5],[4,4],[4,3],[4,2],[4,1],[3,1],[2,1],[1,1],[0,1],[4,0],[3,0],[2,0],[1,0],[0,0]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= rows, cols &lt;= 100</code></li>
	<li><code>0 &lt;= rStart &lt; rows</code></li>
	<li><code>0 &lt;= cStart &lt; cols</code></li>
</ul>

class Solution {
    bool in_range(int row, int col, int ROWS, int COLS) {
        return 0 <= row && row < ROWS && 0 <= col && col < COLS;
    }
public:
    vector<vector<int>> spiralMatrixIII(int rows, int cols, int rStart, int cStart) {
        int dir = 1;
        int path_len = 1;
        int cnt_elem = 0;

        vector<vector<int>> coordinates(rows*cols);
        vector<vector<int>> dirs = {{0,1}, {1,0}, {0,-1}, {-1,0}};
        

        while (cnt_elem < rows*cols) {
            
            for (int i = 0; i < path_len; i++) {
                if (in_range(rStart, cStart, rows, cols)) {
                    coordinates[cnt_elem] = {rStart, cStart};
                    cnt_elem++;
                }
                rStart += dirs[(dir-1) % 4][0];
                cStart += dirs[(dir-1) % 4][1];
            }

            if (dir % 2 == 0) path_len++;
            dir++;
        }

        return coordinates;

    }
};
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