1. G R Lockwood, 2006 1
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Sort the sequence 6, 5, 8, 3, 2, 7, 1Sort the sequence 6, 5, 8, 3, 2, 7, 1
using merge sortusing merge sort

2. G R Lockwood, 2006 2
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Split the sequenceSplit the sequence
atat mm==((ii++jj)/2)/2
 ii=1,=1, jj=7,=7, mm=4=4
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3. G R Lockwood, 2006 3
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Make a recursiveMake a recursive
call to merge sortcall to merge sort
 mm :=:= ((ii++jj)/2)/2==
2.52.5=2=2
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4. G R Lockwood, 2006 4
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Now sorting thisNow sorting this
partpart
 ii=1,=1, jj=2,=2, mm=1 and=1 and
make a recursivemake a recursive
callcall
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5. G R Lockwood, 2006 5
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Sequence of lengthSequence of length
1 is already sorted,1 is already sorted,
so returnso return
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6. G R Lockwood, 2006 6
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Sequence of lengthSequence of length
1 is sorted1 is sorted
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7. G R Lockwood, 2006 7
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Return control andReturn control and
merge these 2 sub-merge these 2 sub-
sequences intosequences into
correct ordercorrect order
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8. G R Lockwood, 2006 8
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Now sort theNow sort the
second part of thissecond part of this
subsequencesubsequence
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9. G R Lockwood, 2006 9
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Sequence of lengthSequence of length
1 is sorted1 is sorted
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10. G R Lockwood, 2006 10
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Sequence of lengthSequence of length
1 is sorted1 is sorted
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11. G R Lockwood, 2006 11
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Merge these twoMerge these two
into correct orderinto correct order
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12. G R Lockwood, 2006 12
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Return control toReturn control to
previous call.previous call.
 Now merge theseNow merge these
two sub-sequencestwo sub-sequences
into correct orderinto correct order
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13. G R Lockwood, 2006 13
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 The recursive callThe recursive call
at line 7 is nowat line 7 is now
completedcompleted
 First part ofFirst part of
sequence is nowsequence is now
fully sortedfully sorted
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14. G R Lockwood, 2006 14
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Control nowControl now
returns to the veryreturns to the very
first call of mergefirst call of merge
sortsort
 A recursive call isA recursive call is
now made on thenow made on the
second part of thesecond part of the
sequencesequence
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15. G R Lockwood, 2006 15
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 ii=5,=5, jj=7,=7, mm=6=6
 Split sequence atSplit sequence at
item 6item 6
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16. G R Lockwood, 2006 16
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Make a recursiveMake a recursive
call to sort thesecall to sort these
two itemstwo items
 Split sequence atSplit sequence at
item 5item 5
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17. G R Lockwood, 2006 17
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Make anotherMake another
recursive call onrecursive call on
the first part of thisthe first part of this
subsequencesubsequence
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18. G R Lockwood, 2006 18
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Sequence of lengthSequence of length
1 is sorted1 is sorted
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19. G R Lockwood, 2006 19
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Make a recursiveMake a recursive
call on second partcall on second part
of sequenceof sequence
 Sequence of lengthSequence of length
1 is sorted1 is sorted
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20. G R Lockwood, 2006 20
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Now merge these 2Now merge these 2
sub-sequencessub-sequences
into correct orderinto correct order
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21. G R Lockwood, 2006 21
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Make a recursiveMake a recursive
call with thecall with the
remaining elementremaining element
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22. G R Lockwood, 2006 22
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Sequence of lengthSequence of length
1 is sorted1 is sorted
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23. G R Lockwood, 2006 23
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Now merge these 2Now merge these 2
sub-sequences intosub-sequences into
correct ordercorrect order
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24. G R Lockwood, 2006 24
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Return to the firstReturn to the first
callcall
 Now merge these 2Now merge these 2
sub-sequences intosub-sequences into
correct ordercorrect order
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25. G R Lockwood, 2006 25
Sorting a Sequence With Merge SortSorting a Sequence With Merge Sort
 Merge sort isMerge sort is
completedcompleted
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