<p>In an&nbsp;<code>n*n</code>&nbsp;grid, there is a snake that spans 2 cells and starts moving from the top left corner at <code>(0, 0)</code> and <code>(0, 1)</code>. The grid has empty cells represented by zeros and blocked cells represented by ones. The snake wants to reach the lower right corner at&nbsp;<code>(n-1, n-2)</code>&nbsp;and&nbsp;<code>(n-1, n-1)</code>.</p>

<p>In one move the snake can:</p>

<ul>
	<li>Move one cell to the right&nbsp;if there are no blocked cells there. This move keeps the horizontal/vertical position of the snake as it is.</li>
	<li>Move down one cell&nbsp;if there are no blocked cells there. This move keeps the horizontal/vertical position of the snake as it is.</li>
	<li>Rotate clockwise if it&#39;s in a horizontal position and the two cells under it are both empty. In that case the snake moves from&nbsp;<code>(r, c)</code>&nbsp;and&nbsp;<code>(r, c+1)</code>&nbsp;to&nbsp;<code>(r, c)</code>&nbsp;and&nbsp;<code>(r+1, c)</code>.<br />
	<img alt="" src="https://assets.leetcode.com/uploads/2019/09/24/image-2.png" style="width: 300px; height: 134px;" /></li>
	<li>Rotate counterclockwise&nbsp;if it&#39;s in a vertical position and the two cells to its right are both empty. In that case the snake moves from&nbsp;<code>(r, c)</code>&nbsp;and&nbsp;<code>(r+1, c)</code>&nbsp;to&nbsp;<code>(r, c)</code>&nbsp;and&nbsp;<code>(r, c+1)</code>.<br />
	<img alt="" src="https://assets.leetcode.com/uploads/2019/09/24/image-1.png" style="width: 300px; height: 121px;" /></li>
</ul>

<p>Return the minimum number of moves to reach the target.</p>

<p>If there is no way to reach the target, return&nbsp;<code>-1</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<p><strong><img alt="" src="https://assets.leetcode.com/uploads/2019/09/24/image.png" style="width: 400px; height: 439px;" /></strong></p>

<pre>
<strong>Input:</strong> grid = [[0,0,0,0,0,1],
               [1,1,0,0,1,0],
&nbsp;              [0,0,0,0,1,1],
&nbsp;              [0,0,1,0,1,0],
&nbsp;              [0,1,1,0,0,0],
&nbsp;              [0,1,1,0,0,0]]
<strong>Output:</strong> 11
<strong>Explanation:
</strong>One possible solution is [right, right, rotate clockwise, right, down, down, down, down, rotate counterclockwise, right, down].
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> grid = [[0,0,1,1,1,1],
&nbsp;              [0,0,0,0,1,1],
&nbsp;              [1,1,0,0,0,1],
&nbsp;              [1,1,1,0,0,1],
&nbsp;              [1,1,1,0,0,1],
&nbsp;              [1,1,1,0,0,0]]
<strong>Output:</strong> 9
</pre>

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

<ul>
	<li><code>2 &lt;= n &lt;= 100</code></li>
	<li><code>0 &lt;= grid[i][j] &lt;= 1</code></li>
	<li>It is guaranteed that the snake starts at empty cells.</li>
</ul>

class Solution {
public:
    int n;
    set<vector<int>> visited;
    bool down(vector<vector<int>>& grid, int x, int y, int dir)
    {
        if ( dir == 1 ){
            if ( x+2<n && !grid[x+1][y] && !grid[x+2][y] && !visited.count({x+1,y,dir}) ) return 1;
        }
        else{
            if ( x+1<n && y+1<n && !grid[x+1][y] && !grid[x+1][y+1] && !visited.count({x+1,y,dir}) ) return 1;
        }
        return 0;
    }
    bool right(vector<vector<int>>& grid, int x, int y, int dir)
    {
        if ( dir == 1 ){
            if ( y+1<n && x+1<n && !grid[x][y+1] && !grid[x+1][y+1] && !visited.count({x,y+1,dir}) ) return 1;
        }
        else{
            if ( y+2<n && !grid[x][y+1] && !grid[x][y+2] && !visited.count({x,y+1,dir}) ) return 1;
        }
        return 0; 
    }
    bool rota(vector<vector<int>>& grid, int x, int y, int dir)
    {
        if ( dir == 1 ){
            if ( x+1<n && y+1<n && !grid[x][y+1] && !grid[x+1][y+1] && !visited.count({x,y,!dir})) return 1;
        }
        else{
            if ( x+1<n && y+1<n && !grid[x+1][y] && !grid[x+1][y+1] && !visited.count({x,y,!dir})) return 1;
        }
        return 0;
    }
    int minimumMoves(vector<vector<int>>& grid) 
    {
        n = grid.size();
        queue<array<int,3>> mem;
        mem.push({0,0,0});
        int res = 0;
        while( !mem.empty() )
        {
            int m = mem.size();
            while (m--)
            {

                auto cur = mem.front();
                mem.pop();
                if ( visited.count({cur[0],cur[1],cur[2]}) ) continue;

                visited.insert({cur[0],cur[1],cur[2]});
                int x = cur[0], y = cur[1];
                if ( x == n-1 && y == n-2 && cur[2] == 0 ) return res;

                if ( right(grid, x, y, cur[2]) )   mem.push({x,y+1,cur[2]});
                if ( down(grid, x, y, cur[2]) )    mem.push({x+1,y,cur[2]});
                if ( rota(grid, x, y, cur[2]) )    mem.push({x,y,!cur[2]});
            }
            res++;
        }
        return -1;   
    }
};
49000