<p>On an <code>2 x 3</code> board, there are five tiles labeled from <code>1</code> to <code>5</code>, and an empty square represented by <code>0</code>. A <strong>move</strong> consists of choosing <code>0</code> and a 4-directionally adjacent number and swapping it.</p>

<p>The state of the board is solved if and only if the board is <code>[[1,2,3],[4,5,0]]</code>.</p>

<p>Given the puzzle board <code>board</code>, return <em>the least number of moves required so that the state of the board is solved</em>. If it is impossible for the state of the board to be solved, return <code>-1</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/06/29/slide1-grid.jpg" style="width: 244px; height: 165px;" />
<pre>
<strong>Input:</strong> board = [[1,2,3],[4,0,5]]
<strong>Output:</strong> 1
<strong>Explanation:</strong> Swap the 0 and the 5 in one move.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/06/29/slide2-grid.jpg" style="width: 244px; height: 165px;" />
<pre>
<strong>Input:</strong> board = [[1,2,3],[5,4,0]]
<strong>Output:</strong> -1
<strong>Explanation:</strong> No number of moves will make the board solved.
</pre>

<p><strong class="example">Example 3:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/06/29/slide3-grid.jpg" style="width: 244px; height: 165px;" />
<pre>
<strong>Input:</strong> board = [[4,1,2],[5,0,3]]
<strong>Output:</strong> 5
<strong>Explanation:</strong> 5 is the smallest number of moves that solves the board.
An example path:
After move 0: [[4,1,2],[5,0,3]]
After move 1: [[4,1,2],[0,5,3]]
After move 2: [[0,1,2],[4,5,3]]
After move 3: [[1,0,2],[4,5,3]]
After move 4: [[1,2,0],[4,5,3]]
After move 5: [[1,2,3],[4,5,0]]
</pre>

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

<ul>
	<li><code>board.length == 2</code></li>
	<li><code>board[i].length == 3</code></li>
	<li><code>0 &lt;= board[i][j] &lt;= 5</code></li>
	<li>Each value <code>board[i][j]</code> is <strong>unique</strong>.</li>
</ul>

class Solution {
public:
    int slidingPuzzle(vector<vector<int>>& board) {
        int n=2;
        int m=3;
        set< vector<vector<int>> >st;
        st.insert(board);
        vector<vector<int>>ans={{1,2,3},
                                 {4,5,0}};
        queue<pair<int,vector<vector<int>> >>q;
        q.push({0,board});
        while(!q.empty()){
         auto it=q.front();
         q.pop();
         int step=it.first;
         vector<vector<int>>vec=it.second;

         if(vec==ans) return step;
         int r,c; 
         for(int i=0;i<n;i++){
             for(int j=0;j<m;j++){
                 if(vec[i][j]==0) {
                  r=i;
                  c=j;
                 }
             }
         } 
         int dr[]={-1,1,0,0};
         int dc[]={0,0,-1,1};
         for(int i=0;i<4;i++){
             vector<vector<int>>temp=vec; 
             int nr=r+dr[i];
             int nc=c+dc[i];
    if(nr>=0 && nr<n && nc>=0 && nc<m){
        swap(temp[r][c],temp[nr][nc]);
        if(st.find(temp)==st.end()){
            st.insert(temp);
             q.push({step+1,temp});
        }  
      }         
         }

        }   
    return -1;
    }
};
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