# Shortest Path in Binary Matrix

In an N by N square grid, each cell is either empty (0) or blocked (1).

A *clear path from top-left to bottom-right* has length`k`if and only if it is composed of cells`C_1, C_2, ..., C_k` such that:

* Adjacent cells

  `C_i`

  and

  `C_{i+1}`

  are connected 8-directionally (ie., they are different and share an edge or corner)
* `C_1`

  is at location

  `(0, 0)`

  (ie. has value

  `grid[0][0]`

  )
* `C_k`

   is at location

  `(N-1, N-1)`

  (ie. has value

  `grid[N-1][N-1]`

  )
* If

  `C_i`

  is located at 

  `(r, c)`

  , then

  `grid[r][c]`

  is empty (ie. 

  `grid[r][c] == 0`

  ).

Return the length of the shortest such clear path from top-left to bottom-right. If such a path does not exist, return -1.

```
public class Solution {
    public int ShortestPathBinaryMatrix(int[][] grid) {
        int m = grid.Length;
        int n = grid[0].Length;

        if(grid[0][0] == 1 || grid[m-1][n-1] == 1){
            return -1;
        }
        bool[][] isVisited = new bool[m][];
        for(int i = 0; i < m ; i++){
            isVisited[i] = new bool[n];
        }

        Queue<int[]> q = new Queue<int[]>();

        q.Enqueue(new int[]{0, 0});
        isVisited[0][0] = true;

        int[][] dirs = new int[8][];

        dirs[0] = new int[]{-1, 0};
        dirs[1] = new int[]{1, 0};
        dirs[2] = new int[]{0, -1};
        dirs[3] = new int[]{0, 1};
        dirs[4] = new int[]{-1,-1};
        dirs[5] = new int[]{1,-1};
        dirs[6] = new int[]{-1, 1};
        dirs[7] = new int[]{1,1};

        int ans = 0;

        while(q.Count > 0){
            int size = q.Count;

            for(int l=0 ;l <size;l++) {

                var curr = q.Dequeue();

                if(curr[0] == m - 1 && curr[1] == n -1){
                    return ans + 1;
                }
                for(int i = 0; i < 8; i++){
                    int x = curr[0] + dirs[i][0];
                    int y = curr[1] + dirs[i][1];

                    if(x < 0 || x >= m || y < 0 || y >= m || isVisited[x][y] || grid[x][y] == 1){
                        continue;
                    }
                    q.Enqueue(new int[]{x, y});
                    isVisited[x][y] = true;
                }
            }
            ans ++; 
        }
        return -1;
    }
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://liuxue2010.gitbook.io/data-structure-and-algorithms/dynamic-programming-i/shortest-path-in-binary-matrix.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.