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Heapsort.py
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Heapsort.py
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def swap(a, i, j):
a[i], a[j] = a[j], a[i]
def is_heap(a):
n = 0
m = 0
while True:
for i in [0, 1]:
m += 1
if m >= len(a):
return True
if a[m] > a[n]:
return False
n += 1
def sift_down(a, n, max):
while True:
biggest = n
c1 = 2*n + 1
c2 = c1 + 1
for c in [c1, c2]:
if c < max and a[c] > a[biggest]:
biggest = c
if biggest == n:
return
swap(a, n, biggest)
n = biggest
def heapify(a):
i = len(a) / 2 - 1
max = len(a)
while i >= 0:
sift_down(a, i, max)
i -= 1
def heapsort(a):
heapify(a)
j = len(a) - 1
while j > 0:
swap(a, 0, j)
sift_down(a, 0, j)
j -= 1
a = [12, 11, 10, 9, 8, 7, 1, 2, 3, 4, 5, 6]
heapsort(a)
print a