How should I practice Robot Navigation Around Lasers?

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Problem · Array

Robot Navigation Around Lasers

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Problem statement

A robot starts at the 1-indexed cell (curRow, curCol) of a numRows by numCols board. Each laser is given by its center cell. A cell is unsafe if its row or its column contains at least one laser.

Choose exactly one of the four cardinal directions and move the robot in a straight line. The robot may enter only safe cells and may not leave the board. Return the maximum number of steps it can take before its next step would enter an unsafe cell or leave the board. The starting cell is not counted as a step.

Function

maxSafeSteps(numRows: int, numCols: int, curRow: int, curCol: int, laserCoordinates: int[][]) → int

Examples

Example 1

numRows = 6numCols = 7curRow = 4curCol = 3laserCoordinates = [[2,6],[6,5]]return = 2

Rows 2 and 6 and columns 5 and 6 are unsafe. From (4,3), the robot can move two cells up, one cell down, one cell right, or two cells left. The maximum is 2.

Example 2

numRows = 4numCols = 5curRow = 2curCol = 3laserCoordinates = [[4,1]]return = 2

Only row 4 and column 1 are unsafe. Moving right reaches columns 4 and 5, for two safe steps.

Constraints

1 <= numRows, numCols <= 200000.
1 <= curRow <= numRows and 1 <= curCol <= numCols.
0 <= laserCoordinates.length <= 200000.
Every laser coordinate is a valid board cell.
The robot's starting cell is safe.