Find Path in a Grid

You are given a grid represented by a 2D matrix of integers where each cell can either be walkable (represented by 0) or blocked by a wall (represented by 1). Your task is to determine whether there exists a path from a starting cell to an ending cell using only adjacent moves (up, down, left, right).

The problem can be modeled as finding a path on a grid graph. Note that a move from cell \( (x, y) \) to an adjacent cell is allowed only if the target cell is within the grid bounds and is walkable.

For example, given the grid below:

[ \begin{matrix} 0 & 0 & 1 & 0 \ 0 & 1 & 0 & 0 \ 0 & 0 & 0 & 1 \ 0 & 1 & 0 & 0 \end{matrix} ]

and starting position \( (0, 0) \) and ending position \( (3, 3) \), a valid path exists. However, if the grid is modified such that the obstacles block the path, then no valid path can be found.

inputFormat

The input is given via stdin with the following format:

R C
row1
row2
... 
rowR
start_x start_y
end_x end_y

Where:

• R and C are integers denoting the number of rows and columns in the grid.
• Each of the next R lines contains C integers (0 or 1) separated by spaces representing the grid.
• \(start_x\) and \(start_y\) specify the starting coordinates (0-indexed).
• \(end_x\) and \(end_y\) specify the target coordinates (0-indexed).

outputFormat

Output a single line to stdout:

• Print YES if there exists a path from the starting position to the ending position, otherwise print NO.

## sample

4 4
0 0 1 0
0 1 0 0
0 0 0 1
0 1 0 0
0 0
3 3

YES

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