Python Example – Write a Python program to sort a list of elements using Cycle sort.

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(Python Example for Citizen Data Scientist & Business Analyst)

 

Write a Python program to sort a list of elements using Cycle sort.

Cycle sort is an in-place, unstable sorting algorithm, a comparison sort that is theoretically optimal in terms of the total number of writes to the original array, unlike any other in-place sorting algorithm. It is based on the idea that the permutation to be sorted can be factored into cycles, which can individually be rotated to give a sorted result.

 

Sample Solution:

Python Code:


def cycleSort(vector):
    "Sort a vector in place and return the number of writes."
    writes = 0
 
    for cycleStart, item in enumerate(vector):
 
        pos = cycleStart
        for item2 in vector[cycleStart + 1:]:
            if item2 < item:
                pos += 1
 
        if pos == cycleStart:
            continue
 
        while item == vector[pos]:
            pos += 1
        vector[pos], item = item, vector[pos]
        writes += 1
 
        while pos != cycleStart:
 
            pos = cycleStart
            for item2 in vector[cycleStart + 1:]:
                if item2 < item:
                    pos += 1
 
            while item == vector[pos]:
                pos += 1
            vector[pos], item = item, vector[pos]
            writes += 1
 
    return writes
 
 
if __name__ == '__main__':
    x = [0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]
    xcopy = x[::]
    writes = cycleSort(xcopy)
    if xcopy != sorted(x):
        print('Wrong order!')
    else:
        print('%rnIs correctly sorted using cycleSort to'
              'n%rnUsing %i writes.' % (x, xcopy, writes))

Sample Output:

[0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]
Is correctly sorted using cycleSort to
[0, 0, 1, 1, 2, 2, 2, 2, 3.5, 4, 5, 6, 7, 8, 9]
Using 10 writes.

 

Write a Python program to sort a list of elements using Cycle sort

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