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46 lines
863 B
Python
46 lines
863 B
Python
def merge(a,b,m,e):
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l=a[b:m+1]
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r=a[m+1:e+1]
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k=b
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i=0
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j=0
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while i<len(l) and j<len(r):
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#change sign for Descending order
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if l[i]<r[j]:
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a[k]=l[i]
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i+=1
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else:
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a[k]=r[j]
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j+=1
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k+=1
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while i<len(l):
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a[k]=l[i]
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i+=1
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k+=1
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while j<len(r):
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a[k]=r[j]
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j+=1
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k+=1
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return a
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def mergesort(a,b,e):
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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 b<e:
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m = (b+e)//2
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#print("ms1",a,b,m)
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mergesort(a,b,m)
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#print("ms2",a,m+1,e)
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mergesort(a,m+1,e)
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#print("m",a,b,m,e)
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merge(a,b,m,e)
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return a
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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