How should I practice Safest Shortest Path Through a Grid?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Snowflake online assessment problems in FastPrep.

Is Safest Shortest Path Through a Grid associated with Snowflake?

FastPrep tags this as a Snowflake online assessment coding practice problem when the problem catalog has that company and stage context.

Safest Shortest Path Through a Grid

Snowflake● HardFULLTIMEOA

Problem statement

You are given a rectangular binary grid and two open cells, start and target. A 0 is an open cell and a 1 is a blocked cell. Coordinates use [row,column] with zero-based indices.

For this exercise, move one cell up, down, left, or right through open cells. Each move costs one step. Blocked cells cannot be entered.

Choose the route

First, minimize the number of moves from start to target.
Among routes with that minimum number of moves, maximize their clearance from blocked cells.

A cell's clearance is its minimum Manhattan distance to any blocked cell. The Manhattan distance from (r,c) to (x,y) is |r-x| + |c-y|; it is measured directly, without routing around obstacles. A route's clearance is the smallest cell clearance along the route, including both endpoints.

Return [moves,clearance] for the chosen route. Return [-1,-1] if no route exists. If the grid has no blocked cells, use -1 for clearance because there is no obstacle to measure from. If start == target, the route has 0 moves and includes that one cell.

Function

safestShortestPath(grid: int[][], start: int[], target: int[]) → int[]

Examples

Example 1

grid = [[0,0,0,0,0],[0,0,0,0,0],[0,0,1,0,0],[0,0,0,0,0],[0,0,0,0,0]]start = [0,0]target = [4,4]return = [8,2]

A route along the top row and right edge uses 8 moves and stays at least 2 cells from the blocked center. Every route needs at least 8 moves, and no shortest route can keep a larger clearance.

Example 2

grid = [[0,0,0,0,0],[0,0,0,0,0],[0,0,1,0,0],[0,0,0,0,0],[0,0,0,0,0]]start = [2,0]target = [2,4]return = [6,1]

The blocked center forces a detour. A shortest route uses 6 moves and passes next to the obstacle, so its clearance is 1. A route with clearance 2 would need 8 moves and loses because fewer moves come first.

Example 3

grid = [[0,1],[1,0]]start = [0,0]target = [1,1]return = [-1,-1]

Both neighbors of the start are blocked, so the target cannot be reached. Return [-1,-1].

Constraints

1 <= grid.length <= 80.
1 <= grid[0].length <= 80.
Every row has the same length, and every entry is 0 or 1.
start.length == target.length == 2.
Both coordinates are inside the grid and name open cells.