<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 minimumMoves(vector<vector<int>>& grid) {
        int n=grid.size();
        auto target=make_pair(n*n-2,n*n-1);
        queue<pair<int, int>> q;
        q.emplace(0,1);
        bool vis[n*n][2];
        memset(vis,0,sizeof vis);
        vis[0][0]=true;

        auto move=[&](int i1,int j1, int i2, int j2){
            if (i1 >= 0 && i1 < n && j1 >= 0 && j1 < n && i2 >= 0 && i2 < n && j2 >= 0 && j2 < n) {
                int a = i1 * n + j1, b = i2 * n + j2;
                int status = i1 == i2 ? 0 : 1;
                if (!vis[a][status] && grid[i1][j1] == 0 && grid[i2][j2] == 0) {
                    q.emplace(a, b);
                    vis[a][status] = true;
            }
        }
    };
    int ans = 0;
        while (!q.empty()) {
            for (int k = q.size(); k; --k) {
                auto p = q.front();
                q.pop();
                if (p == target) {
                    return ans;
                }
                auto [a, b] = p;
                int i1 = a / n, j1 = a % n;
                int i2 = b / n, j2 = b % n;
                move(i1, j1 + 1, i2, j2 + 1);
                move(i1 + 1, j1, i2 + 1, j2);
                if (i1 == i2 && i1 + 1 < n && grid[i1 + 1][j2] == 0) {
                    move(i1, j1, i1 + 1, j1);
                }
                if (j1 == j2 && j1 + 1 < n && grid[i2][j1 + 1] == 0) {
                    move(i1, j1, i1, j1 + 1);
                }
            }
            ++ans;
        }
        return -1;
    }
};
16600