[Leetcode] 499. The Maze III 解题报告

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于 2017-12-06 11:38:25 发布 · 2.7k 阅读

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#Leetcode #解题报告 #DFS #BFS

本篇博客详细介绍了LeetCode第499题《The Maze III》的解题报告，讨论了如何找到从球的初始位置到洞的最短距离，并确保移动顺序是字典序最小的。文章提到了两种解题方法：深度优先搜索(DFS)和广度优先搜索(BFS)，并提供了DFS的解决方案。在DFS中，作者强调了如何维护当前的最短路径和字典序最小路径，并解释了如何在遇到障碍时改变方向。虽然DFS是解决方案之一，但BFS可能通过使用PriorityQueue实现更高的效率。

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题目：

There is a ball in a maze with empty spaces and walls. The ball can go through empty spaces by rolling up (u), down (d), left (l) or right(r), but it won't stop rolling until hitting a wall. When the ball stops, it could choose the next direction. There is also a hole in this maze. The ball will drop into the hole if it rolls on to the hole.

Given the ball position, the hole position and the maze, find out how the ball could drop into the hole by moving the shortest distance. The distance is defined by the number of empty spaces traveled by the ball from the start position (excluded) to the hole (included). Output the moving directions by using 'u', 'd', 'l' and 'r'. Since there could be several different shortest ways, you should output the lexicographically smallest way. If the ball cannot reach the hole, output "impossible".

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