How should I practice Mouse and Cheese Reachability?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Meta onsite interview problems in FastPrep.

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Mouse and Cheese Reachability

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Problem statement

A mouse starts at coordinate (0, 0) in a finite rectangular environment. The environment is serialized as grid for this function runner:

'.' is an open cell.
'#' is a blocked cell.
'C' is the unique open cell containing cheese.

A movement oracle move(x, y) accepts only an orthogonally adjacent absolute coordinate. It returns false and leaves the mouse in place when that coordinate is blocked or outside the grid; otherwise it moves the mouse and returns true. A goal oracle reachCheese() returns whether the current cell contains the cheese.

Return whether some sequence of successful oracle moves can reach the cheese. The serialized grid defines exactly the same movement outcomes, so you may compute the result directly from it.

Function

canReachCheese(grid: String[]) → boolean

Examples

Example 1

grid = ["..#",".#C","..."]return = true

The mouse can move down to row 2, cross to column 2, and then move up to the cheese.

Example 2

grid = [".#C","###","..."]return = false

The blocked cells separate the starting cell from the cheese.

Example 3

grid = ["C"]return = true

The mouse begins on the cheese, so no movement is needed.

Constraints

1 <= grid.length <= 500.
1 <= grid[0].length <= 500.
Every row has the same length.
Every cell is '.', '#', or 'C'.
grid[0][0] is open or contains cheese.
Exactly one cell contains 'C'.