Create find-minimum-time-to-reach-last-room-ii.py

Author: kamyu104

Python/find-minimum-time-to-reach-last-room-ii.py

@@ -0,0 +1,34 @@
+# Time:  O(n * m * logn(n * m))
+# Space: O(n * m)
+
+import heapq
+
+
+# dijkstra's algorithm
+class Solution(object):
+    def minTimeToReach(self, moveTime):
+        """
+        :type moveTime: List[List[int]]
+        :rtype: int
+        """
+        def dijkstra(start, target):
+            DIRECTIONS = [(1, 0), (0, 1), (-1, 0), (0, -1)]
+            dist = [[float("inf")]*len(moveTime[0]) for _ in xrange(len(moveTime))]
+            dist[start[0]][start[1]] = 0
+            min_heap = [(dist[start[0]][start[1]], start[0], start[1])]
+            while min_heap:
+                curr, i, j = heapq.heappop(min_heap)
+                if curr != dist[i][j]:
+                    continue
+                if (i, j) == target:
+                    break
+                for di, dj in DIRECTIONS:
+                    ni, nj = i+di, j+dj
+                    c = (i+j)%2+1
+                    if not (0 <= ni < len(moveTime) and 0 <= nj < len(moveTime[0]) and dist[ni][nj] > max(moveTime[ni][nj], curr)+c):
+                        continue
+                    dist[ni][nj] = max(moveTime[ni][nj], curr)+c
+                    heapq.heappush(min_heap, (dist[ni][nj], ni, nj))
+            return dist[target[0]][target[1]]
+    
+        return dijkstra((0, 0), (len(moveTime)-1, len(moveTime[0])-1))