<p>Given an <code>n x n</code> binary matrix <code>grid</code>, return <em>the length of the shortest <strong>clear path</strong> in the matrix</em>. If there is no clear path, return <code>-1</code>.</p>

<p>A <strong>clear path</strong> in a binary matrix is a path from the <strong>top-left</strong> cell (i.e., <code>(0, 0)</code>) to the <strong>bottom-right</strong> cell (i.e., <code>(n - 1, n - 1)</code>) such that:</p>

<ul>
	<li>All the visited cells of the path are <code>0</code>.</li>
	<li>All the adjacent cells of the path are <strong>8-directionally</strong> connected (i.e., they are different and they share an edge or a corner).</li>
</ul>

<p>The <strong>length of a clear path</strong> is the number of visited cells of this path.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/example1_1.png" style="width: 500px; height: 234px;" />
<pre>
<strong>Input:</strong> grid = [[0,1],[1,0]]
<strong>Output:</strong> 2
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/example2_1.png" style="height: 216px; width: 500px;" />
<pre>
<strong>Input:</strong> grid = [[0,0,0],[1,1,0],[1,1,0]]
<strong>Output:</strong> 4
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> grid = [[1,0,0],[1,1,0],[1,1,0]]
<strong>Output:</strong> -1
</pre>

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

<ul>
	<li><code>n == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= n &lt;= 100</code></li>
	<li><code>grid[i][j] is 0 or 1</code></li>
</ul>

class Solution {
public:
    int maxX = 0;
    int maxY = 0;

    void addIfValid(vector <pair<int,int>> &vec, int x, int y) {
        if (x >-1 && y > -1 && x <= maxX && y <= maxY) {
            vec.emplace_back(make_pair(x, y));
        }
    }

    vector<pair<int,int>> getN(int x, int y) {
        vector<pair<int,int>> retVal;
        addIfValid(retVal, x+1, y-1);
        addIfValid(retVal, x+1, y);
        addIfValid(retVal, x+1, y+1);
        addIfValid(retVal, x-1, y-1);
        addIfValid(retVal, x-1, y);
        addIfValid(retVal, x-1, y+1);
        addIfValid(retVal, x, y-1);
        addIfValid(retVal, x, y+1);
        return retVal;
    }
    

    int shortestPathBinaryMatrix(vector<vector<int>>& grid) {
        map<pair<int,int>,int> weights;
        queue<pair<int,int>> pointsQ;

        maxX = grid.size() -1;
        maxY = grid[0].size()-1;
        int length = -1;

        if (grid[maxX][maxY] == 0) {
            pointsQ.push({maxX, maxY});
            weights[{maxX, maxY}] = 1;

            while (!pointsQ.empty()) {
                auto top = pointsQ.front();
                pointsQ.pop();

                for (auto neigh: getN(top.first, top.second)) {                    
                    if (grid[neigh.first][neigh.second] != 0) continue;

                    if (!weights.contains(neigh)) {                        
                        weights.insert({neigh, weights[top] +1});
                        pointsQ.push(neigh);
                    } else {
                        if (weights [top] + 1 < weights[neigh]) {
                            pointsQ.push(neigh);
                            weights[neigh] = weights [top] + 1;
                        }
                    }
                }

                if (weights.contains({0,0}))
                    length = weights[{0, 0}];
            }
        }

        return length;



    }
};
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