<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 shortestPathBinaryMatrix(vector<vector<int>>& grid) {
        int n = grid.size();
        if(grid[0][0] == 1 || grid[n-1][n-1] == 1)return -1;
        vector<vector<bool>> vis(n, vector<bool>(n, false));

        queue<pair<int, int>> q;
        q.push({0, 0});

        vector<pair<int, int>> dv = {
            {-1, -1}, {-1, 0}, {-1, 1}, 
            {0, -1}, {0, 1}, 
            {1, -1}, {1, 0}, {1, 1}
        };
        
        int sol = 1;
        while(!q.empty()){
            int size = q.size();

            while(size--){
                int x = q.front().first;
                int y = q.front().second;
                q.pop();

                if(vis[x][y])continue;
                vis[x][y]=1;
                if(x == n-1 && y == n-1)return sol;
                if(grid[x][y]==1)continue;

                for(auto [dx, dy]: dv){
                    int i = x+dx, j = y+dy;
                    if(i >= 0 && i < n && j >= 0 && j < n){
                        if(grid[i][j]==1 || vis[i][j])continue;
                        q.push({i, j});
                    }
                }
            }
            sol++;
        }

        return -1;
    }
};
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