3248. Snake in Matrix

Problem

There is a snake in an n x n matrix grid and can move in four possible directions. Each cell in the grid is identified by the position: grid[i][j] = (i * n) + j.

The snake starts at cell 0 and follows a sequence of commands.

You are given an integer n representing the size of the grid and an array of strings commands where each command[i] is either "UP", "RIGHT", "DOWN", and "LEFT". It’s guaranteed that the snake will remain within the grid boundaries throughout its movement.

Return the position of the final cell where the snake ends up after executing commands.

https://leetcode.cn/problems/snake-in-matrix/

Example 1:

Input: n = 2, commands = ["RIGHT","DOWN"]
Output: 3
Explanation:

Example 2:

Input: n = 3, commands = ["DOWN","RIGHT","UP"]
Output: 1
Explanation:

Constraints:

• 2 <= n <= 10
• 1 <= commands.length <= 100
• commands consists only of "UP", "RIGHT", "DOWN", and "LEFT".
• The input is generated such the snake will not move outside of the boundaries.

Test Cases

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class Solution:
    def finalPositionOfSnake(self, n: int, commands: List[str]) -> int:

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import pytest

from solution import Solution


@pytest.mark.parametrize('n, commands, expected', [
    (2, ["RIGHT","DOWN"], 3),
    (3, ["DOWN","RIGHT","UP"], 1),
])
class Test:
    def test_solution(self, n, commands, expected):
        sol = Solution()
        assert sol.finalPositionOfSnake(n, commands) == expected

Thoughts

i = j = 0。

• UP: i--
• RIGHT: j++
• DOWN: i++
• LEFT: j--

Code

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class Solution:
    def finalPositionOfSnake(self, n: int, commands: list[str]) -> int:
        i = j = 0
        for cmd in commands:
            if cmd == 'UP':
                i -= 1
            elif cmd == 'RIGHT':
                j += 1
            elif cmd == 'DOWN':
                i += 1
            else:
                j -= 1

        return (i * n) + j

许可协议

本文除了题目描述（Problem）部分之外，其他内容由 Calf 原创，采用 CC BY-NC-SA 4.0 许可协议，转载请注明出处。

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