update readme

Author: hogan-tech

0505-the-maze-ii/0505-the-maze-ii.py

@@ -1,33 +1,47 @@
-from collections import deque
-import heapq
+# time complexity: O(m*n*log(m*n))
+# space complexity: O(m*n)
+from collections import defaultdict
+from heapq import heappop, heappush
 from typing import List
 
 
 class Solution:
     def shortestDistance(self, maze: List[List[int]], start: List[int], destination: List[int]) -> int:
-        m, n, q, stopped = len(maze), len(maze[0]), [(0, start[0], start[1])], {
-            (start[0], start[1]): 0}
-
-        while q:
-            dist, x, y = heapq.heappop(q)
-            if [x, y] == destination:
-                return dist
-            for i, j in ((-1, 0), (1, 0), (0, -1), (0, 1)):
-                newX, newY, d = x, y, 0
-                while 0 <= newX + i < m and 0 <= newY + j < n and maze[newX + i][newY+j] != 1:
-                    newX += i
-                    newY += j
-                    d += 1
-
-                if (newX, newY) not in stopped or dist + d < stopped[(newX, newY)]:
-                    stopped[(newX, newY)] = dist + d
-                    heapq.heappush(q, (dist + d, newX, newY))
+        ROW = len(maze)
+        COL = len(maze[0])
+        visited = defaultdict(lambda: float('inf'))
+        minHp = [(0, start[0], start[1])]
+        visited[(start[0], start[1])] = 0
+        while minHp:
+            currDist, currR, currC = heappop(minHp)
+            if [currR, currC] == destination:
+                return currDist
+            for dR, dC in [(1, 0), (0, 1), (-1, 0), (0, -1)]:
+                nextR = currR
+                nextC = currC
+                nextDist = currDist
+                while 0 <= nextR + dR < ROW and 0 <= nextC + dC < COL and maze[nextR + dR][nextC + dC] == 0:
+                    nextR += dR
+                    nextC += dC
+                    nextDist += 1
+                if nextDist < visited[(nextR, nextC)]:
+                    heappush(minHp, (nextDist, nextR, nextC))
+                    visited[(nextR, nextC)] = nextDist
         return -1
 
 
 maze = [[0, 0, 1, 0, 0], [0, 0, 0, 0, 0], [
     0, 0, 0, 1, 0], [1, 1, 0, 1, 1], [0, 0, 0, 0, 0]]
 start = [0, 4]
 destination = [4, 4]
-
+print(Solution().shortestDistance(maze, start, destination))
+maze = [[0, 0, 1, 0, 0], [0, 0, 0, 0, 0], [
+    0, 0, 0, 1, 0], [1, 1, 0, 1, 1], [0, 0, 0, 0, 0]]
+start = [0, 4]
+destination = [3, 2]
+print(Solution().shortestDistance(maze, start, destination))
+maze = [[0, 0, 0, 0, 0], [1, 1, 0, 0, 1], [
+    0, 0, 0, 0, 0], [0, 1, 0, 0, 1], [0, 1, 0, 0, 0]]
+start = [4, 3]
+destination = [0, 1]
 print(Solution().shortestDistance(maze, start, destination))

0505-the-maze-ii/README.md

@@ -115,35 +115,3 @@ It helps others discover the repo and keeps the project growing.
 ---
 
 Feedback / Questions → open an Issue or reach out on [LinkedIn](https://www.linkedin.com/in/hogan-l/)  
-
-<!---LeetCode Topics Start-->
-# LeetCode Topics
-## Array
-|  |
-| ------- |
-| [0505-the-maze-ii](https://github.com/hogan-tech/leetcode-solution/tree/master/0505-the-maze-ii) |
-## Depth-First Search
-|  |
-| ------- |
-| [0505-the-maze-ii](https://github.com/hogan-tech/leetcode-solution/tree/master/0505-the-maze-ii) |
-## Breadth-First Search
-|  |
-| ------- |
-| [0505-the-maze-ii](https://github.com/hogan-tech/leetcode-solution/tree/master/0505-the-maze-ii) |
-## Graph
-|  |
-| ------- |
-| [0505-the-maze-ii](https://github.com/hogan-tech/leetcode-solution/tree/master/0505-the-maze-ii) |
-## Heap (Priority Queue)
-|  |
-| ------- |
-| [0505-the-maze-ii](https://github.com/hogan-tech/leetcode-solution/tree/master/0505-the-maze-ii) |
-## Matrix
-|  |
-| ------- |
-| [0505-the-maze-ii](https://github.com/hogan-tech/leetcode-solution/tree/master/0505-the-maze-ii) |
-## Shortest Path
-|  |
-| ------- |
-| [0505-the-maze-ii](https://github.com/hogan-tech/leetcode-solution/tree/master/0505-the-maze-ii) |
-<!---LeetCode Topics End-->

Python/0505-the-maze-ii.py

@@ -1,30 +1,33 @@
-<h2><a href="https://leetcode.com/problems/the-maze-ii/">505. The Maze II</a></h2><h3>Medium</h3><hr><div><p>There is a ball in a <code>maze</code> with empty spaces (represented as <code>0</code>) and walls (represented as <code>1</code>). The ball can go through the empty spaces by rolling <strong>up, down, left or right</strong>, but it won't stop rolling until hitting a wall. When the ball stops, it could choose the next direction.</p>
+<h2><a href="https://leetcode.com/problems/the-maze-ii">505. The Maze II</a></h2><h3>Medium</h3><hr><p>There is a ball in a <code>maze</code> with empty spaces (represented as <code>0</code>) and walls (represented as <code>1</code>). The ball can go through the empty spaces by rolling <strong>up, down, left or right</strong>, but it won&#39;t stop rolling until hitting a wall. When the ball stops, it could choose the next direction.</p>
 
-<p>Given the <code>m x n</code> <code>maze</code>, the ball's <code>start</code> position and the <code>destination</code>, where <code>start = [start<sub>row</sub>, start<sub>col</sub>]</code> and <code>destination = [destination<sub>row</sub>, destination<sub>col</sub>]</code>, return <em>the shortest <strong>distance</strong> for the ball to stop at the destination</em>. If the ball cannot stop at <code>destination</code>, return <code>-1</code>.</p>
+<p>Given the <code>m x n</code> <code>maze</code>, the ball&#39;s <code>start</code> position and the <code>destination</code>, where <code>start = [start<sub>row</sub>, start<sub>col</sub>]</code> and <code>destination = [destination<sub>row</sub>, destination<sub>col</sub>]</code>, return <em>the shortest <strong>distance</strong> for the ball to stop at the destination</em>. If the ball cannot stop at <code>destination</code>, return <code>-1</code>.</p>
 
 <p>The <strong>distance</strong> is the number of <strong>empty spaces</strong> traveled by the ball from the start position (excluded) to the destination (included).</p>
 
 <p>You may assume that <strong>the borders of the maze are all walls</strong> (see examples).</p>
 
 <p>&nbsp;</p>
 <p><strong class="example">Example 1:</strong></p>
-<img alt="" src="https://assets.leetcode.com/uploads/2021/03/31/maze1-1-grid.jpg" style="width: 573px; height: 573px;">
-<pre><strong>Input:</strong> maze = [[0,0,1,0,0],[0,0,0,0,0],[0,0,0,1,0],[1,1,0,1,1],[0,0,0,0,0]], start = [0,4], destination = [4,4]
+<img alt="" src="https://assets.leetcode.com/uploads/2021/03/31/maze1-1-grid.jpg" style="width: 573px; height: 573px;" />
+<pre>
+<strong>Input:</strong> maze = [[0,0,1,0,0],[0,0,0,0,0],[0,0,0,1,0],[1,1,0,1,1],[0,0,0,0,0]], start = [0,4], destination = [4,4]
 <strong>Output:</strong> 12
 <strong>Explanation:</strong> One possible way is : left -&gt; down -&gt; left -&gt; down -&gt; right -&gt; down -&gt; right.
 The length of the path is 1 + 1 + 3 + 1 + 2 + 2 + 2 = 12.
 </pre>
 
 <p><strong class="example">Example 2:</strong></p>
-<img alt="" src="https://assets.leetcode.com/uploads/2021/03/31/maze1-2-grid.jpg" style="width: 573px; height: 573px;">
-<pre><strong>Input:</strong> maze = [[0,0,1,0,0],[0,0,0,0,0],[0,0,0,1,0],[1,1,0,1,1],[0,0,0,0,0]], start = [0,4], destination = [3,2]
+<img alt="" src="https://assets.leetcode.com/uploads/2021/03/31/maze1-2-grid.jpg" style="width: 573px; height: 573px;" />
+<pre>
+<strong>Input:</strong> maze = [[0,0,1,0,0],[0,0,0,0,0],[0,0,0,1,0],[1,1,0,1,1],[0,0,0,0,0]], start = [0,4], destination = [3,2]
 <strong>Output:</strong> -1
 <strong>Explanation:</strong> There is no way for the ball to stop at the destination. Notice that you can pass through the destination but you cannot stop there.
 </pre>
 
 <p><strong class="example">Example 3:</strong></p>
 
-<pre><strong>Input:</strong> maze = [[0,0,0,0,0],[1,1,0,0,1],[0,0,0,0,0],[0,1,0,0,1],[0,1,0,0,0]], start = [4,3], destination = [0,1]
+<pre>
+<strong>Input:</strong> maze = [[0,0,0,0,0],[1,1,0,0,1],[0,0,0,0,0],[0,1,0,0,1],[0,1,0,0,0]], start = [4,3], destination = [0,1]
 <strong>Output:</strong> -1
 </pre>
 
@@ -43,4 +46,3 @@ The length of the path is 1 + 1 + 3 + 1 + 2 + 2 + 2 = 12.
 	<li>Both the ball and the destination exist in an empty space, and they will not be in the same position initially.</li>
 	<li>The maze contains <strong>at least 2 empty spaces</strong>.</li>
 </ul>
-</div>