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Create BitonicSort.py (TheAlgorithms#386)
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Aruj-Sharma authored and poyea committed Feb 11, 2019
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# Python program for Bitonic Sort. Note that this program
# works only when size of input is a power of 2.

# The parameter dir indicates the sorting direction, ASCENDING
# or DESCENDING; if (a[i] > a[j]) agrees with the direction,
# then a[i] and a[j] are interchanged.*/
def compAndSwap(a, i, j, dire):
if (dire == 1 and a[i] > a[j]) or (dire == 0 and a[i] < a[j]):
a[i], a[j] = a[j], a[i]

# It recursively sorts a bitonic sequence in ascending order,


# if dir = 1, and in descending order otherwise (means dir=0).
# The sequence to be sorted starts at index position low,
# the parameter cnt is the number of elements to be sorted.
def bitonicMerge(a, low, cnt, dire):
if cnt > 1:
k = int(cnt / 2)
for i in range(low, low + k):
compAndSwap(a, i, i + k, dire)
bitonicMerge(a, low, k, dire)
bitonicMerge(a, low + k, k, dire)

# This funcion first produces a bitonic sequence by recursively


# sorting its two halves in opposite sorting orders, and then
# calls bitonicMerge to make them in the same order
def bitonicSort(a, low, cnt, dire):
if cnt > 1:
k = int(cnt / 2)
bitonicSort(a, low, k, 1)
bitonicSort(a, low + k, k, 0)
bitonicMerge(a, low, cnt, dire)

# Caller of bitonicSort for sorting the entire array of length N


# in ASCENDING order
def sort(a, N, up):
bitonicSort(a, 0, N, up)


# Driver code to test above
a = []

n = int(input())
for i in range(n):
a.append(int(input()))
up = 1

sort(a, n, up)
print("\n\nSorted array is")
for i in range(n):
print("%d" % a[i])

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