<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) {
        priority_queue<vector<long long>,vector<vector<long long>>,greater<vector<long long>>>pq;
        pq.push({1,0,0});

        vector<int>dx={-1,0,+1,0,-1,-1,+1,+1};
        vector<int>dy={0,-1,0,+1,-1,+1,-1,+1};
        int n=grid.size();
        int m=grid[0].size();
        vector<vector<long long>>dist(n,vector<long long>(m,INT_MAX));
        if(grid[0][0]==1) return -1;
        dist[0][0]=1;
        while(!pq.empty()){
            vector<long long>v=pq.top();
            pq.pop();
            long long dis=v[0];
            int x=v[1];
            int y=v[2];
            for(int k=0;k<8;k++){
                int i=x+dx[k];
                int j=y+dy[k];

                if(i<0 || j<0 || i>=n || j>=m) continue;
                if(grid[i][j]==1) continue;
                if(dist[i][j]<=dis+1) continue;
                dist[i][j]=dis+1;
                pq.push({dist[i][j],i,j});
            }
        }
        if(dist[n-1][m-1]==INT_MAX) return -1;
        return dist[n-1][m-1];
    }
};
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