Summary: We consider a more efficient way to sort values.
a. Make a copy of mergesort.ss, my implementation of merge sort. Scan through the code and make sure that you understand all the procedures.
b. Start DrScheme
a. Write an expresssion to merge the lists
(1 2 3) and
(1 1.5 2.3).
b. Write an expression to merge two lists that contain the same values.
c. Write an expression to merge two lists of strings. (You may choose the strings yourself. Each list should have at least three elements.)
d. Assume that we represent names as lists of the form
Write an expression to merge the following two lists
(define cs-faculty (list (list "Bishop" "David") (list "Gum" "Ben") (list "Rebelsky" "Samuel") (list "Stone" "John") (list "Walker" "Henry"))) (define young-cs-kids (list (list "Rebelsky" "Daniel") (list "Rebelsky" "Jonathan") (list "Rebelsky" "William")))
a. What will happen if you call
merge with unsorted
lists as the first two parameters?
b. Verify your answer by experimentation.
c. What will happen if you call
merge with sorted lists
of very different lengths as the first two parameters?
d. Verify your answer by experimentation.
split to split:
a. A list of numbers of length 6
b. A list of numbers of length 5
c. A list of strings of length 6
merge-sort on a list you design of fifteen integers.
new-merge-sort on a list you design of twenty strings.
c. Uncomment the lines in
new-merge-sort that print out
the current list of lists. Rerun
new-merge-sort on a list
you design of twenty strings. Is the output what you expect?
a. Run both versions of merge sort on the empty list.
b. Run both versions of merge sort on a one-element list.
c. Run both versions of merge sort on a list with duplicate elements.
a. Using DrScheme's built-in timing mechanism (you may have to look through the
online help to find information about that mechanism), make a table of the
running time of insertion sort,
new-merge-sort on inputs of size 0, 10,
100, 1000, 10000, 20000, and 5000.0
b. Graph your data.
c. Based on your data, what can you say about the relative speeds of the three sorting methods?
One of my colleagues prefers to define
like the following
(define split (lambda (ls) (let kernel ((rest ls) (left null) (right null)) (if (null? rest) (list left right) (kernel (cdr rest) (cons (car rest) right) left)))))
a. How does this procedure split the list?
b. Why might you prefer one version of split over the other?
Wednesday, 22 November 2000 [Samuel A. Rebelsky]
Thursday, 26 April 2001 [Samuel A. Rebelsky]
splitto return two lists, rather than a list of lists.
Tuesday, 26 November 2002 [Samuel A. Rebelsky]
splitto return a list of lists.
new-merge-sort, including problem in which students compare the two versions of merge sort.
Monday, 2 December 2002 [Samuel A. Rebelsky]
Wednesday, 4 December 2002 [Samuel A. Rebelsky]
Monday, 28 April 2003 [Samuel A. Rebelsky]
I usually create these pages
on the fly, which means that I rarely
proofread them and they may contain bad grammar and incorrect details.
It also means that I tend to update them regularly (see the history for
more details). Feel free to contact me with any suggestions for changes.
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