2020-03-29

Author: JiayangWu

1162.地图分析/1162-地图分析.py

@@ -0,0 +1,38 @@
+class Solution(object):
+    def maxDistance(self, grid):
+        """
+        :type grid: List[List[int]]
+        :rtype: int
+        """
+        from collections import deque
+        m, n = len(grid), len(grid[0])
+        land = []
+        for i in range(m):
+            for j in range(n):
+                if grid[i][j] == 1:
+                    land.append((i, j))
+
+        if not land or len(land) == m * n:
+            return -1 
+        
+        res = 0
+        dx = [1, -1, 0, 0]
+        dy = [0, 0, 1, -1]
+
+        queue = deque(land)
+        visited = set(land)
+        while queue:
+            for _ in range(len(queue)):
+                x0, y0 = queue.popleft()
+
+                for k in range(4):
+                    x = x0 + dx[k]
+                    y = y0 + dy[k]
+
+                    if 0 <= x < m and 0 <= y < n and grid[x][y] == 0 and (x, y) not in visited:
+                        queue.append((x, y))
+                        visited.add((x, y))
+            res += 1
+        return res - 1
+
+