Midterm Review - CS61B

8/17/2019 Midterm Review - CS61B

1/23

CS61B Midterm Review

Winston Liaw and Amir Kamil


2/23

Midterm Review 2

Agenda1. Static vs. Dynamic

2. Bo and !ointer diagrams

". Code #$estions and eam!les

%. Bit re!resentation

&. Algorit'mic Analysis6. Access rig'ts

(. #$ic)ie *$estions


3/23

Midterm Review 3

Static vs. Dynamic W'at 'a!!ens+ Ass$me we 'ave

de,ned-omer ' / new omer0

Bart 3 / new Bart0

omer '1 / 3'1.tal)20

Answer- omer4 Bart-d$de


4/23

Midterm Review 4

Static vs. Dynamic cont. W'at 'a!!ens+ Ass$me t'e same

de,nitions

Bart 31 / 3

31.tal)20

Cartoon c1 / '

00omerc1.tal)%0

Answer- omer4 Bart-d$de

Answer- omer4 omer- do'5


5/23

Midterm Review 5

Static vs. Dynamic cont. W'at 'a!!ens+

Cartoon c2 / 3

00Bartc2.w'oa0

L$m!y l2 / 3

00omerl2.tal)%0

Answer- d$de

Answer- Bart-

d$de


6/23

Midterm Review 6

Static vs. Dynamic cont. or calls wit' an o37ect o8 interest

0i.e. '.804 static met'ods are called

3ased on static ty!e4 non9staticmet'ods are 3ased on dynamic ty!e

or calls involving :t'is;4 t'ings get

a little tric)ier. Static calls :stay; int'e same class4 dynamic calls are3ased on t'e dynamic set.


7/23 Midterm Review 7

Bo and



Bo and



Bo and / @=2>



Bo and / @=2>

? ?

? ?

? ?

@


11/23

Midterm Review 11

Coding #$estion inis' t'is met'od-

iven an ntList4 it will reverse itdestr$ctively and ret$rn t'e new list

!$3lic ntList reverse0ntList l E

F

G


12/23

Midterm Review 12

Coding #$estion Sol$tion!$3lic ntList reverse0ntList l E

ntList !rev / n$ll

ntList net / l.tail

w'ile 0l 5/ n$ll Enet / l.tail

l.tail / !rev

!rev / l

l / net

Gret$rn !rev once we are done reversing all t'e !ointers

we need to set lHs 'ead to t'e new 'ead

G


13/23

Midterm Review 13

Bit Re!resentation W'at is t'e 3it re!resentation 8or-

3yte 3 / 1&

W'at is t'is val$e as a c'ar+

1?11?111

W'at a3o$t as a 3yte+

Answer- ????1111

Answer- 1I"

Answer- 9("


14/23

Midterm Review 14

Bit Re!resentation Jwos com!lement

8 t'e Most Signi,cant Bit 0MSB is ?4

t'en treat t'e remaining 3its as normal0as a !ositive n$m3er. 8 t'e MSB is 14 i! t'e remaining 3its4

add 14 and t'at is yo$r negative val$e.

Remem3er4 twos com!lement onlya!!lies to signed val$es. or an$nsigned integer4 8or instance4 treat itas :normal.;


15/23

Midterm Review 15

Mod$lar Arit'metic or mod$lar arit'metic-

ind o$t 'ow many times yo$r divisor can

divide into yo$r dividend. Remem3er4 t'eremainder m$st 3e !ositive

8 t'e remainder is greater t'an t'e rangeo8 yo$r val$es 03yte can 'ave val$es 3tw

12I and 12( 8or instance t'en loo!val$e aro$nd


16/23

Midterm Review 16

Anot'er Coding #$estion inis' t'ese met'ods-

ntList !*$e$e

removes t'e node wit' smallest val$e

!$3lic int remove0 E

F

G

inserts t'e val$e into !*$e$e

!$3lic void insert0int ) E

F

G


17/23

Midterm Review 17

Anot'er Coding #$estion

Sol$tion

!$3lic int remove0 E

int / !*$e$e.'ead

!*$e$e / !*$e$e.tail

ret$rn

G


18/23

Midterm Review 18

Anot'er Coding #$estion

Sol$tion cont.!$3lic void insert0int ) E

ntList tem! / !*$e$e

ntList !rev / n$ll

w'ile 0tem! 5/ n$ll E

i8 0) N tem!.'ead E i8 0!rev 5/ n$ll E

!rev.tail / new ntList0)4 tem!

G else E

!*$e$e / new ntList0)4 !*$e$e

G

ret$rn

G else E

!rev / tem!

tem! / tem!.tail

G

G


19/23

Midterm Review 19

Algorit'mic Analysis De,nition o8 Big9O'

O0g0n / E80n - t'ere eist !ositive

constants c and n? s$c' t'at? N/ 80n N/ cg0n 8or all n P/ n?

De,nition o8 Big9Omega Ω0g0n / E80n - t'ere eist !ositive

constants c and n? s$c' t'at

? N/ cg0n N/ 80n 8or all n P/ n?


20/23

Midterm Review 20

Algorit'mic Analysis One met'od ta)es O0n24 w'ile

anot'er ta)es O0n lg0n. J'e O0n

lg0n met'od is always !re8erred.

Jr$e or 8alse+


21/23

Midterm Review 21

Algorit'mic Analysis W'at are t'e r$nning times 0Big9O'4

Big9Omega4 Big9J'eta 8or t'is code+

8or 0int i / ) i N @ iQQ E

8or 0int 7 / ? 7 N @ 7QQ E

some lg 0n code 'ereG

GAnswer- all are 0@9)0@lg0n


22/23

Midterm Review 22

Access rig'ts 8 yo$ override a met'od in a c'ild class4

ava allows yo$ to c'ange t'e access

rig'ts to 3e less restrictive

.


23/23

Midterm Review 23

#$ic)ies W'at class 'as no s$!erclass+

W'y wo$ld yo$ want to !ic) anarray over a list+

Midterm Review - CS61B

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