<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;
    queue<vector<int>> q;
    
    void down(vector<vector<int>>& g, vector<int>& A){
        int r1 = A[0], c1 = A[1], r2 = A[2], c2 = A[3];
        if(r1 < n - 1 && !g[r1 + 1][c1] && r2 < n - 1 && !g[r2 + 1][c2])
            q.push({r1 + 1, c1, r2 + 1, c2});
    }
    void right(vector<vector<int>>& g, vector<int>& A){
        int r1 = A[0], c1 = A[1], r2 = A[2], c2 = A[3];
        if(c1 < n - 1 && !g[r1][c1 + 1] && c2 < n - 1 && !g[r2][c2 + 1])
            q.push({r1, c1 + 1, r2, c2 + 1});
    }
    
    void clockwise(vector<vector<int>>& g, vector<int>& A){
        int r1 = A[0], c1 = A[1], r2 = A[2], c2 = A[3];
        if(r1 != r2) return;
        if(r1 < n - 1 && !g[r1 + 1][c1] && !g[r1 + 1][c2])
            q.push({r1, c1, r1 + 1, c1});
    }
    void counterClockwise(vector<vector<int>>& g, vector<int>& A){
        int r1 = A[0], c1 = A[1], r2 = A[2], c2 = A[3];
        if(c1 != c2) return;
        if(c1 < n - 1 && !g[r1][c1 + 1] && !g[r2][c1 + 1])
            q.push({r1, c1, r1, c1 + 1});
    }
    set<vector<int>> set;
    
    int minimumMoves(vector<vector<int>>& g) {
        n = g.size();
        q.push({0, 0, 0, 1});
        int level = 0;
        while(!q.empty()){
            int sz = q.size();
            for(int i = 0; i < sz; i++){
                auto A = q.front();
                q.pop();
                if(set.find(A) != set.end()) continue;
                set.insert(A);
                int r1 = A[0], c1 = A[1], r2 = A[2], c2 = A[3];
                if(r1 == n - 1 && c1 == n - 2 && r2 == n - 1 && c2 == n - 1)    return level;
                down(g, A); right(g, A);
                clockwise(g, A); counterClockwise(g, A);
            }
            level++;
        }
        return -1;
    }
};
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