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findMinSwaps.py
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findMinSwaps.py
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# This Python file uses the following encoding: utf-8
# Python3 program to find
# minimum number of swaps
# required to sort an array
# Function returns the minimum
# number of swaps required to
# sort the array
def minSwaps(arr):
n = len(arr)
# Create two arrays and use
# as pairs where first array
# is element and second array
# is position of first element
arrpos = [*enumerate(arr)]
# Sort the array by array element
# values to get right position of
# every element as the elements
# of second array.
arrpos.sort(key = lambda it : it[1])
# To keep track of visited elements.
# Initialize all elements as not
# visited or false.
vis = {k : False for k in range(n)}
# Initialize result
ans = 0
for i in range(n):
# alreadt swapped or
# alreadt present at
# correct position
if vis[i] or arrpos[i][0] == i:
continue
# find number of nodes
# in this cycle and
# add it to ans
cycle_size = 0
j = i
while not vis[j]:
# mark node as visited
vis[j] = True
# move to next node
j = arrpos[j][0]
cycle_size += 1
# update answer by adding
# current cycle
if cycle_size > 0:
ans += (cycle_size - 1)
# return answer
return ans
# Driver Code
arr = [4, 1, 2, 3]
print(minSwaps(arr))