Turtle Navigation on Grid

EasyPython

Problem

Wix Studio can model editor interactions on a bounded square grid. Given an N x N grid, a starting cell, an initial facing direction, and a command sequence, compute the final position and facing direction.

Commands have the following meanings:

F: Move forward one cell. If the next cell is outside the grid, remain in the current cell.
L: Turn 90 degrees left without changing position.
R: Turn 90 degrees right without changing position.

Use zero-based coordinates, where (0, 0) is the northwest corner. Directions are represented by N, E, S, and W.

Formal Specification

Implement final_position(n, start, direction, commands):

n is an integer grid size.
start is a two-element list [row, column].
direction is one of N, E, S, or W.
commands is a string containing only F, L, and R.
Return a dictionary with keys row, col, and direction.

Constraints

1 <= n <= 10^6
0 <= start[0], start[1] < n
0 <= len(commands) <= 10^7
The input contains only valid directions and commands.
The grid does not wrap around.

Function Signature

def final_position(n, start, direction, commands):

Commands have the following meanings:

F: Move forward one cell. If the next cell is outside the grid, remain in the current cell.
L: Turn 90 degrees left without changing position.
R: Turn 90 degrees right without changing position.

Use zero-based coordinates, where (0, 0) is the northwest corner. Directions are represented by N, E, S, and W.

Formal Specification

Implement final_position(n, start, direction, commands):

n is an integer grid size.
start is a two-element list [row, column].
direction is one of N, E, S, or W.
commands is a string containing only F, L, and R.
Return a dictionary with keys row, col, and direction.