clrs chp6

優先隊列的實現

class heap:
    def __init__(self,A):
        self.A=A
        self.size=0
        self.length=len(A)-1
    def build(self):
        build_max_heap(self)
    def __setitem__(self,i,x):
        self.A[i]=x
    def __getitem__(self,i):
        return self.A[i]
    def __repr__(self):
        return ' '.join([str(self.A[i]) for i in range(0,self.size+1)])
def Parent(i):
    return i//2
def Left(i):
    return 2*i
def Right(i):
    return 2*i+1
def max_heapify(A,i):
    l=Left(i)
    r=Right(i)
    if l<=A.size and A[l]>A[i]:
        largest=l
    else: largest=i
    if r<=A.size and A[r]>A[largest]:
        largest=r
    if largest!=i:
        A[largest],A[i]=A[i],A[largest]
        max_heapify(A,largest)
def build_max_heap(A):
    A.size=A.length
    for i in range(A.length//2,0,-1):
        max_heapify(A,i)
def heap_sort(A):
    build_max_heap(A)
    for i in range(A.length,1,-1):
        A[i],A[1]=A[1],A[i]
        A.size-=1
        max_heapify(A,1)
def max_elem(A):
    if A.size<1:
        raise ValueError("heap underflow")
    else:
        return A[1]
def extract_max(A):
    if A.size<1:
        raise ValueError("heap underflow")
    maxv=A[1]
    A[1]=A[A.size]
    A.size-=1
    max_heapify(A,1)
    return maxv
def increase_key(A,i,key):
    if key<A[i]:
        raise ValueError("new key is smaller than current key")
    A[i]=key
    while i>1 and A[Parent(i)]<A[i]:
        A[i],A[Parent(i)]=A[Parent(i)],A[i]
        i=Parent(i)
def heap_insert(A,key):
    A.size+=1
    infinity=10000000
    A[A.size]=-infinity
    increase_key(A,A.size,key)
#class priority_queue:
    #def __init__(self,lst=[]):
        #self.lst=lst
    #def insert(x):
lst=['error',4,1,3,2,16,9,10,14,8,7]
h=heap(lst)
h.build()
print(h)
increase_key(h,9,15)
print(h)
extract_max(h)
print(h)
heap_insert(h,100)
print(h)