def mergeKLists(self, lists):
"""
:type lists: List[ListNode]
:rtype: ListNode
"""
if not lists:
return None
st = PriorityQueue()
for x in lists:
if x:
st.push(x, x.val)
if st.size() == 0:
return None
head = tail = None
while st.size() != 0:
ptr = st.pop()
if ptr.next:
st.push(ptr.next, ptr.next.val)
ptr.next = None
if ptr == None:
continue
if tail == None:
head = ptr
else:
tail.next = ptr
tail = ptr
tail.next = None
return head
def buildPriorityQueue(freq_table):
PriorityQueue = MinNodePriorityQueue()
for item, freq in freq_table.iteritems():
# print ("added %s: %d"%(item, freq))
PriorityQueue.push(Node(item, freq))
return PriorityQueue
