<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) {
        map<pair<int,int>,bool>vis;
        vector<pair<int,int>>sis={{0,1},{-1,1},{-1,0},{-1,-1},{0,-1},{1,-1},{1,0},{1,1}};
        int n=grid.size();
        map<pair<int,int>,int>dis;
        queue<pair<pair<int,int>,int>>q;
        if(grid[0][0]==0){
            q.push({{0,0},0});
            vis[{0,0}]=1;
        }
        
        while(!q.empty()){
            int pr=q.front().first.first;
            int pc=q.front().first.second;
            int pdis=q.front().second;
            q.pop();
            for(auto x:sis){
                int cr=pr+x.first;
                int cc=pc+x.second;
                if(cr<n&&cr>=0&&cc<n&&cc>=0&&vis[{cr,cc}]==0&&grid[cr][cc]==0){
                    vis[{cr,cc}]=1;
                    q.push({{cr,cc},pdis+1});
                    dis[{cr,cc}]=pdis+1;
                }
            }
        }
        if(vis[{n-1,n-1}])return dis[{n-1,n-1}]+1;
        else return -1;
    }
};
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