<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) {
        queue<vector<int>> q;
        set<vector<int>> st;
        int m = grid.size(), n = grid.back().size();
        q.push({0, 0, 0});
        st.insert({0, 0, 0});
        vector<int> term{m - 1, m - 2, 0};
        int step = 0;
        while (q.size()) {
            for (int i = q.size(); i > 0; --i) {
                auto cur = q.front(); q.pop(); 
                int x = cur[0], y = cur[1], v = cur[2];
                int ax, ay;
                if (v) {
                    if (x + 2 < m and grid[x + 2][y] == 0) {
                        vector<int> next{x + 1, y, 1};
                        if (!st.count(next)) {
                            st.insert(next);
                            q.push(next);
                        }
                    }
                    if (y + 1 < n and grid[x][y + 1] == 0 and grid[x + 1][y + 1] == 0) {
                        vector<int> next({x, y + 1, 1});
                        if (!st.count(next)) {
                            st.insert(next);
                            q.push(next);
                        }
                    }
                    if (y + 1 < n and x + 1 < n and grid[x][y + 1] == 0 and grid[x + 1][y + 1] == 0) {
                        vector<int> next({x, y, 0});
                        if (!st.count(next)) {
                            st.insert(next);
                            q.push(next);
                        }
                    }
                }
                else {
                    if (x + 1 < m and grid[x + 1][y] == 0 and grid[x + 1][y + 1] == 0) {
                        vector<int> next{x + 1, y, 0};
                        if (next == term) {
                            return step + 1; 
                        }
                        if (!st.count(next)) {
                            st.insert(next);
                            q.push(next);
                        }
                    }
                    if (y + 2 < n and grid[x][y + 2] == 0) {
                        vector<int> next({x, y + 1, 0});
                        if (next == term)
                            return step + 1;
                        if (!st.count(next)) {
                            st.insert(next);
                            q.push(next);
                        }
                    }
                    if (x + 1 < n and y + 1 < n and grid[x + 1][y] == 0 and grid[x + 1][y + 1] == 0) {
                        vector<int> next({x, y, 1});
                        if (!st.count(next)) {
                            st.insert(next);
                            q.push(next);
                        }
                    }

                }
            }
            step++;
        }
        return -1;
    }
};
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