def trapRainWater(heightMap):
"""
:type heightMap: List[List[int]]
:rtype: int
"""
if not heightMap or not heightMap[0]:
return 0
direction = [(1, 0), (-1, 0), (0, 1), (0, -1)]
m, n = len(heightMap), len(heightMap[0])
heap = []
visited = set()
# Push all the blocks on the border into heap. And create a visit array.
for i in range(m):
for j in range(n):
if i == 0 or i == m - 1 or j == 0 or j == n - 1:
heapq.heapqpush(heap, (heightMap[i][j], i, j))
visited.add((i, j))
res = 0
while heap:
cur_height, x, y = heapq.heappop(heap)
for dir in direction:
r, c = x + dir[0], y + dir[1]
if r < 0 or r >= m or c < 0 or c >= n or (r, c) in visited:
continue
res += max(0, cur_height - heightMap[r][c])
heapq.heapqpush(heap, (max(cur_height, heightMap[r][c]), r, c))
visited.add((r, c))
return res
def dijkstra(start):
q = []
heapq.heapqpush(q, (0, start))
distance[start] = 0
while q:
dist, now = heapq.heaqpop(q)
if distance[now] < dist:
continue
for i in graph[now]:
cost = dist + i[1]
if cost < distance[i[0]]:
distance[i[0]] = cost
heapq.heappush(q, (cost, i[0]))
def mergeSortedArr(sortedArrs):
sortedArrIters = [iter(x) for x in sortedArrs]
minHeap = []
for i, it in enumerate(sortedArrIters):
firstElement = next(it, None)
if firstElement is not None:
heapq.heappush(minHeap, (firstElement, i))
result = []
while minHeap:
smallestEntry, smallestArrIndex = heapq.heappop(minHeap)
smallestIter = sortedArrIters[smallestArrIndex]
result.append(smallestEntry)
nextElement = next(smallestIter, None)
if nextElement is not None:
heapq.heapqpush(minHeap, (nextElement, smallestArrIndex))
return result
def _put(self, item):
heapq.heapqpush(self.queue, item)