Update 0994-腐烂的橘子.py

Author: zaie

0994.腐烂的橘子/0994-腐烂的橘子.py

@@ -1,43 +1,23 @@
-class Solution(object):
-    def orangesRotting(self, grid):
-        """
-        :type grid: List[List[int]]
-        :rtype: int
-        """
-        from collections import deque
-        if not grid or not grid[0]:
-            return 0
-        
-        m, n = len(grid), len(grid[0])
-        dx = [1, -1, 0, 0]
-        dy = [0, 0, 1, -1]
-        
-        queue = deque()
-        for i in range(m):
-            for j in range(n):
-                if grid[i][j] == 2:
-                    queue.append((i, j))
+1. 首先分别将腐烂的橘子和新鲜的橘子保存在两个集合中；
+2. 模拟广度优先搜索的过程，方法是判断在每个腐烂橘子的四个方向上是否有新鲜橘子，如果有就腐烂它。
+每腐烂一次时间加 1，并剔除新鲜集合里腐烂的橘子；
+3. 当橘子全部腐烂时结束循环。
 
-        res = 0
-        while queue:     
-            for i in range(len(queue)):
-                pair = queue.popleft()
-                x0, y0 = pair[0], pair[1]
-                for k in range(4):
-                    x = x0 + dx[k]
-                    y = y0 + dy[k]
+class Solution:
+    def orangesRotting(self, grid: List[List[int]]) -> int:
+        row = len(grid)
+        col = len(grid[0])
+        rotten = {(i, j) for i in range(row) for j in range(col) if grid[i][j] == 2} # 腐烂集合
+        fresh = {(i, j) for i in range(row) for j in range(col) if grid[i][j] == 1}  # 新鲜集合
+        time = 0
+        while fresh:
+            if not rotten: return -1
+            rotten = {(i + di, j + dj) for i, j in rotten for di, dj in [(0, 1), (0, -1), (1, 0), (-1, 0)] if (i + di, j + dj) in fresh} # 即将腐烂的如果在新鲜的集合中，就将它腐烂
+            fresh -= rotten # 剔除腐烂的
+            time += 1
+        return time
 
-                    if 0 <= x < m and 0 <= y < n and grid[x][y] == 1:
-                        grid[x][y] = 2
-                        queue.append((x, y))
-            if not queue:
-                break
-            res += 1
-        for i in range(m):
-            for j in range(n):
-                if grid[i][j] == 1:
-                    return -1
-        return res
-                    
-        
-        
+作者：z1m
+链接：https://leetcode.cn/problems/rotting-oranges/solution/yan-du-you-xian-sou-suo-python3-c-by-z1m/
+来源：力扣（LeetCode）
+著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。