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025b1a6989
* Update Merge sort variable names * Update mergesort.py * Update mergesort.py * black * Update mergesort.py Co-authored-by: Christian Clauss <cclauss@me.com>
52 lines
1.3 KiB
Python
52 lines
1.3 KiB
Python
def merge(arr, left, mid, right):
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# overall array will divided into 2 array
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# left_arr contains the left portion of array from left to mid
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# right_arr contains the right portion of array from mid + 1 to right
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left_arr = arr[left : mid + 1]
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right_arr = arr[mid + 1 : right + 1]
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k = left
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i = 0
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j = 0
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while i < len(left_arr) and j < len(right_arr):
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# change sign for Descending order
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if left_arr[i] < right_arr[j]:
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arr[k] = left_arr[i]
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i += 1
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else:
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arr[k] = right_arr[j]
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j += 1
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k += 1
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while i < len(left_arr):
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arr[k] = left_arr[i]
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i += 1
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k += 1
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while j < len(right_arr):
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arr[k] = right_arr[j]
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j += 1
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k += 1
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return arr
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def mergesort(arr, left, right):
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"""
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>>> mergesort([3, 2, 1], 0, 2)
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[1, 2, 3]
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>>> mergesort([3, 2, 1, 0, 1, 2, 3, 5, 4], 0, 8)
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[0, 1, 1, 2, 2, 3, 3, 4, 5]
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"""
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if left < right:
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mid = (left + right) // 2
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# print("ms1",a,b,m)
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mergesort(arr, left, mid)
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# print("ms2",a,m+1,e)
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mergesort(arr, mid + 1, right)
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# print("m",a,b,m,e)
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merge(arr, left, mid, right)
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return arr
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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