Arrays: Arrays: FIT100 FIT100 FIT100 Just a thought FIT100 - - PDF document

FIT100 FIT100 FIT100

Arrays: Arrays:

Indexing a Collection of Items

D.A. Cle me nts

FIT100 FIT100 FIT100

Just a thought…

FIT100 FIT100 FIT100

Arrays

• I

nde xing

∗ Cre a ting a nd using lists, o r a rra ys

Cre a ting a nd using lists, o r a rra ys

• Pro c e ssing a n a rra y

∗ E

le me nt b y e le me nt

∗ E

le me nt b y e le me nt

• Arra y me tho ds

Q i k k ith li t

∗ Quic k wo rk with lists

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INDE XING

Cre a ting a nd using lists, o r a rra ys

INDE XING

What is an Array?

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• An inde xe d list o f ite ms, o r e le me nts
• I

nde xe d me a ns e a c h e le me nt in the list ha s a numb e r o r inde x numb e r, o r inde x

• 14. Ja me s Buc ha na n

15 Ab ra ha m L inc o ln 1. Ge o rg e Wa shing to n 2 Jo hn Ada ms

• 28. Wa rre n Ha rding

29 Ca lvin Co o lidg e

• 15. Ab ra ha m L

inc o ln

• 16. Andre w Jo hnso n
• 17. Ulysse s S. Gra nt
• 18. Ruthe rfo rd B Ha ye s

2. Jo hn Ada ms 3. T ho ma s Je ffe rso n 4. Ja me s Ma diso n 5. Ja me s Mo nro e

• 29. Ca lvin Co o lidg e
• 30. He rb e rt Ho o ve r
• 31. F

ra nklin D. Ro o se ve lt

• 32. Ha rry S. T

ruma n

• 19. Ja me s Ga rfie ld
• 20. Che ste r Arthur
• 21. Gro ve r Cle ve la nd

22 B j i H i 6. Jo hn Quinc y Ada ms 7. Andre w Ja c kso n 8. Ma rtin Va n Bure n 9 Willi H i

• 33. Dwig ht E

ise nho we r

• 34. Jo hn K

e nne dy

• 35. L

yndo n Jo hnso n 36 Ri h d Ni

• 22. Be nja min Ha rriso n
• 23. Gro ve r Cle ve la nd
• 24. Willia m Mc K

inle y 25 T he o do re 9. Willia m Ha rriso n

• 10. Jo hn T

yle r

• 11. Ja me s Po lk

12 Za c ha ry T a ylo r

• 36. Ric ha rd Nixo n
• 37. Ge ra ld F
• rd
• 38. Ja me s Ca rte r

39 Ro na ld Re a g a n

• 25. T

he o do re Ro o se ve lt

• 26. Willia m H. T

a ft

• 27. Wo o dro w Wilso n
• 12. Za c ha ry T

a ylo r

• 13. Milla rd F

illmo re

• 14. Franklin Pierce
• 39. Ro na ld Re a g a n
• 40. Ge o rg e H. W. Bush
• 41. Willia m Clinto n
• 42. Ge o rg e W. Bush

FIT100 FIT100 FIT100

Indexing

• Pro c e ss o f c re a ting a se q ue nc e o f na me s b y

a sso c ia ting a b a se na me with a numb e r (like Apo llo 13 o r He nry VI I I )

∗ E

a c h inde xe d ite m is c a lle d a n e le me nt o f the b a se - na me d se q ue nc e

• I

nde x Synta x

• I

nde x Synta x

∗ inde x numb e r is e nc lo se d in sq ua re b ra c ke ts [ ]

• I

te ra tio ns c a n b e use d to re fe r to a ll e le me nts o f I te ra tio ns c a n b e use d to re fe r to a ll e le me nts o f a na me

∗ A[j] fo r suc c e ssive ite ra tio ns o ve r j re fe rring to

diffe re nt e le me nts o f A diffe re nt e le me nts o f A

FIT100 FIT100 FIT100

Indexing (cont'd)

• I

nde x Orig in

∗ T

he po int a t whic h inde xing b e g ins p g g (the le a st inde x)

∗ I

n life , the first e le me nt ma y b e g in with I n life , the first e le me nt ma y b e g in with 1, o r ha ve no numb e r (Que e n E liza b e th)

∗ Ja va Sc ript always use s inde x o rig in 0

FIT100 FIT100 FIT100

• Arra ys a re va ria b le s initia lize d b y

Rules for Arrays

• Arra ys a re va ria b le s initia lize d b y

new Array (<number of elements>);

• <numb e r o f e le me nts> is numb e r o f ite ms in
• <numb e r o f e le me nts> is numb e r o f ite ms in

;

• Arra y inde xing b e g ins a t 0

Arra y inde xing b e g ins a t 0

• Gre a te st inde x is

<numb e r o f e le me nts> - 1

• Numb e r o f e le me nts is a rra y le ng th
• I

nde x va lue s ra ng e fro m 0 to (le ng th – 1) I nde x va lue s ra ng e fro m 0 to (le ng th 1)

FIT100 FIT100 FIT100

Array Reference Syntax

• Arra y re fe re nc e is a rra y na me

to g e the r with inde x e nc lo se d in b ra c ke ts (no n-ne g a tive inte g e r o r e xpre ssio n o r va ria b le tha t re so lve s to no n-ne g a tive inte g e r)

array[i] y[ ]

FIT100 FIT100 FIT100

Array Reference Syntax

• T

he Wo rld-F a mo us I te ra tio n, o r 0-o rig in lo o p ite ra tio n, is pe rfe c t fo r lo o ping thro ug h a rra ys

∗ Sta rt a t 0 ∗ I

nc re me nt b y 1 to pro c e ss e ve ry e le me nt in the a rra y

• Use the inc re me nting va ria b le a s the inde x fo r the

a rra y e le me nt

∗ E

nd whe n yo u re a c h the la st e le me nt in the

∗ E

nd whe n yo u re a c h the la st e le me nt in the a rra y

FIT100 FIT100 FIT100

PR OCE SSING AN AR R AY

E le me nt b y e le me nt

PR OCE SSING AN AR R AY

f L R l

FIT100 FIT100 FIT100

for Loops Rule

• T

he Wo rld-F a mo us I te ra tio n fo r lo o ping thro ug h a n a rra y: g y

for ( i = 0; i < fruits.length; i++ ) { alert(fruits[i]); }

• .length is a b uilt-in Ja va Sc ript pro pe rty

i f tha t a lwa ys g ive s yo u the le ng th o f a n a rra y

∗ Length of an array is the number of elements

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Demonstration

• Looping through the fruits array

Processing elements in an

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Processing elements in an array

var i, text=""; //declare iteration and other variables var fruits = new Array( 'l ' ' l ' ' ' 't i ' 'k t ' 'lemons','apples','mangoes','tangerines','kumquats', 'cantaloupe','peaches','grapefruit','raspberries'); alert("Total number of fruits is " + fruits.length); for (i=0; i<fruits.length; i++) { text += i + '. ' + fruits[i] + '<br />'; [ ] ; } document.write("<h1>Elements of Fruits Array:</h1><p>" + text + "</p>"); text + </p> );

A M th d

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Arra y Me tho ds: .push

• Add mo re fruits to the a rra y with .push

var i, text=""; //declare iteration and other variables , ; var fruits = new Array( 'lemons','apples','mangoes','tangerines','kumquats','cantaloupe', 'peaches' 'grapefruit' 'raspberries'); peaches , grapefruit , raspberries );

• fruits. push('bananas','oranges','pears');

alert("Total number of fruits is " + fruits.length); f (i 0 i<f it l th i++) for (i=0; i<fruits.length; i++) { text += i + '. ' + fruits[i] + '<br />'; } document.write("<h1>Elements of Fruits Array:</h1><p>" + text + "</p>");

for Loops Rule!

FIT100 FIT100 FIT100

• Afte r a dding mo re e le me nts to o ur

a rra y do e s o ur fo r lo o p still wo rk? a rra y, do e s o ur fo r lo o p still wo rk?

for ( i = 0; i < fruits.length; i++ ) { alert(fruits[i]); }

• Ye s! fruits.length still ta ke s us to

the e nd o f the fruits a rra y— the e nd o f the fruits a rra y wha te ve r its le ng th.

A M h d

FIT100 FIT100 FIT100

Array Methods: push

• Verify it by looping through the

expanded fruits array p y

FIT100 FIT100 FIT100

AR R AY ME T HODS

Quic k wo rk with lists

AR R AY ME T HODS

FIT100 FIT100 FIT100

Array Methods = Possibilities!

push

• push

∗ a dds e le me nts to the a rra y

fruits push(‘ b a na na s’ ’ ne c ta rine s’ ’ a pple s’ ); fruits.push( b a na na s , ne c ta rine s , a pple s );

• pop

∗ pulls the la st e le me nt o ff o f the a rra y ∗ pulls the la st e le me nt o ff o f the a rra y

fruits.po p();

• c onc at

c onc at

∗ c o mb ine s se ve ra l a rra ys into o ne ∗ No te : c o pie s o f the a rra ys a re use d ∗ T

he o rig ina l a rra ys re ma in a nd a re una ffe c te d fruits.c o nc a t(c itrus,sto ne F ruit,b e rrie s);

Array Methods = Possibilities!

FIT100 FIT100 FIT100

y

join

• join

∗ c o mb ine s a ll e le me nts into a string , se pa ra te d b y

c o mma s o r a s spe c ifie d: fruits.jo in(;); c o mma s o r a s spe c ifie d: fruits.jo in(;);

• sor

t

∗ so rts the e le me nts in the a rra y

so s e e e e s e a a y fruits.so rt(); / / a lwa ys a sc e nding

• r

e ve r se

∗ re ve rse s the e le me nts in a n a rra y ∗ Use d with so rt to so rt de sc e nding

fruits.so rt(); / / so rts into a sc e nding o rde r fruits.re ve rse (); / / re ve rse s to de sc e nding

FIT100 FIT100 FIT100

Array Methods = Possibilities!

• toStr

ing

∗ c o nve rts the a rra y to a string

fruits.string ();

Array Method: sort

FIT100 FIT100 FIT100

y

• So rt with.sort

∗ Asc e nding o nly (A-Z, 0-9)

var i, text=""; //declare iteration and other variables var fruits = new Array( 'lemons','apples','mangoes','tangerines','kumquats','cantaloupe', 'peaches','grapefruit','raspberries');

• fruits. push('bananas','oranges','pears');

fruits.sort(); alert("Total number of fruits is " + fruits.length); alert( Total number of fruits is fruits.length); for (i=0; i<fruits.length; i++) { text += i + ' ' + fruits[i] + '<br />'; text += i + . + fruits[i] + <br /> ; } document.write("<h1>Elements of Fruits Array:</h1><p>" + text + "</p>");

FIT100 FIT100 FIT100

Array Sort

• De mo nstra tio n

Sort in Descending Order

FIT100 FIT100 FIT100

Sort in Descending Order

• Re ve rse the so rt with .reverse

var i, text=""; //declare iteration and other variables var fruits = new Array( 'lemons','apples','mangoes','tangerines','kumquats','cantaloupe', 'peaches','grapefruit','raspberries');

• fruits. push('bananas','oranges','pears');

fruits.sort(); fruits.reverse(); alert("Total number of fruits is " + fruits.length); alert( Total number of fruits is fruits.length); for (i=0; i<fruits.length; i++) { text += i + ' ' + fruits[i] + '<br />'; text += i + . + fruits[i] + <br /> ; } document.write("<h1>Elements of Fruits Array:</h1><p>" + text + "</p>");

A M h d

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Array Method: reverse

• De mo nstra tio n

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End papers…

• Why is pro g ra mming fun?
• Se c o nd is the ple a sure o f ma king thing s

Se c o nd is the ple a sure o f ma king thing s tha t a re use ful to o the r pe o ple . De e p within, we wa nt o the rs to use o ur wo rk a nd to find it he lpful. I n this re spe c t the pro g ra mming syste m is no t e sse ntia lly diff t f th hild' fi t l il diffe re nt fro m the c hild's first c la y pe nc il ho lde r “fo r Da ddy's o ffic e .”

So urc e : F re de ric k P. Bro o ks, Jr. T he Mythic al Man-Mo nth: E ssays o n S

• ftware

E ng ine e ring