! Given the following Structure: ! We can define a pointer to a structure. ! Now studentptr points to the s1 structure.

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1 Liked Lists Uit 5 Sectios 11.9 & CS 2308 Fall 2018 Jill Seama 11.9: Poiters to Structures! Give the followig Structure: struct Studet { strig ame; // Studet s ame it idnum; // Studet ID umber it credithours; // Credit hours erolled float ga; // Curret GPA ;! We ca defie a oiter to a structure Studet s1 = { Jae Doe, 12345, 15, 3.3; Studet *studetptr; studetptr = &s1;! Now studetptr oits to the s1 structure.!1!2 Poiters to Structures structure oiter oerator: ->! How to access a member through the oiter? Studet s1 = { Jae Doe, 12345, 15, 3.3; Studet *studetptr; studetptr = &s1; cout << *studetptr.ame << ed;! dot oerator has higher recedece tha the dereferecig oerator, so: *studetptr.ame is equivalet to! You must dereferece the oiter first: cout << (*studetptr).ame << ed; // ERROR studetptr is ot a structure! *(studetptr.ame) // WORKS!3! Due to the awkwardess of the oiter otatio, C rovides a oerator for dereferecig structure oiters: studetptr->ame! The structure oiter oerator is the hyhe (-) followed by the greater tha (>), like a arrow.! I summary: s1.ame is equivalet to // a member of structure s1 (*studetptr).ame str->ame // a member of the structure str oits to!4

2 cout << Name << ame1 << edl; Structure Poiter: examle! Fuctio to iut a studet, usig a tr to struct! Call: void iutstudet(studet *s) { cout << Eter Studet ame: ; getlie(ci,s->ame); cout << Eter studetid: ; ci >> s->idnum; cout << Eter credit hours: ; ci >> s->credithours; cout << Eter GPA: ; ci >> s->ga; Studet s1; iutstudet(&s1); cout << s1.ame << edl;... Or you could use a referece arameter. I m usig a oiter to give a examle of usig the -> sytax.!5 Dyamically Allocatig Structures! Structures ca be dyamically allocated with ew: Studet *str; str = ew Studet; str->ame = Jae Doe ; str->idnum = 12345;... delete str;! Arrays of structures ca also be dyamically allocated: Studet *str; str = ew Studet[100]; str[0].ame = Joh Deer ;... delete [] str; If a oiter oits to a array, you ca use square brackets with it, as if it were a array. Do ot use -> here.! Itroductio to Liked Lists! A data structure reresetig a list! A series of dyamically allocated odes chaied together i sequece - Each ode oits to oe other ode.! A searate oiter (the ) oits to the first item i the list.! The last elemet oits to ull (address 0) ull!7! Each ode cotais: Node Orgaizatio - data members cotai the elemets values. - a oiter that ca oit to aother ode data! We use a struct to defie the ode tye: struct ListNode { double value; ListNode *ext; ;! ext ca hold the address of a ListNode. - it ca also be ull oiter!8

3 Usig (or ulltr) Liked Lists: Tasks! Equivalet to address 0! Used to secify ed of the list! I C++11, you ca use ulltr istead of! is defied i the cstddef er.! to test a oiter for, these are equivalet: while (!= )... <==> while ()... if (==)... <==> if (!)...! Note: Do NOT dereferece a tr! We will imlemet the followig tasks o a liked list: T1: Create a emty list T2: Create a ew ode T3: Add a ew ode to frot of list (give ewnode) T4: Traverse the list (ad outut) T5: Fid the last ode (of a o-emty list) T6: Fid the ode cotaiig a certai value T7: Fid a ode AND it s revious eighbor. T8: Aed to the ed of a o-emty list T9: Delete the first ode T10: Delete a elemet, give ad ListNode * = ; cout << ->value; //crash! ull oiter excetio!9!10 T11: Isert a ew elemet, give ad T1:Create a emty list! let s make the emty list struct ListNode // the ode data tye { double value; // data ListNode *ext; // tr to ext ode ; T2:Create a ew ode:! let s make a ew ode: ListNode *ewnode = ew ListNode; ewnode->value = 1.2; ewnode->ext = ; it mai() { ListNode * = ; // the emty list! It s ot attached to the list yet. ewnode 1.2!11!12

4 T3:Add ew ode to frot of list:! make ewnode s ext oit to the first elemet.! the make oit to ewnode. ewnode ewnode->ext = ; = ewnode; 1.2 This works eve if is, try it. T4:Traverse the list (ad outut all the elemets)! let s outut a list of two elemets: cout << ->value << << ->ext->value << edl;! ow usig a temorary oiter to oit to each ode: ListNode *; //temorary oiter (do t use for this) = ; // oits to the first ode cout << ->value << ; = ->ext; //makes oit to the 2d ode (draw it!) cout << ->value << edl; = ->ext; //what does oit to ow?! ow let s rewrite that as a loo: ListNode *; = ; //temorary oiter (do t use for this) // oits to the first ode ewnode 1.2!13 while (!=) { cout << ->value << ; = ->ext; //makes oit to the ext ode!14 T5:Fid the last ode (of a o-emty list)! Goal: make a temorary oiter,, oit to the last ode i the list. T6:Fid the ode cotaiig a certai value! Goal: make a temorary oiter,, oit to the ode cotaiig 5.6. ull 5.6 ull! Make oit to the first ode. The: - do =->ext util oits to the last ode. - i the last ode, ext is ull. - so sto whe ->ext is ull. ListNode *=; // oits to what oits to while (->ext!=) { = ->ext; //makes oit to the ext ode!15! Make oit to the first ode. The: - do =->ext util oits to the ode with so sto whe ->value is 5.6. ListNode *=; // oits to what oits to while (->value!=5.6) { = ->ext; //makes oit to the ext ode!16

5 Fid the ode cotaiig a certai value, cotiued! What if 5.6 is ot i the list?! If 5.6 is ot i the list, the loo will ot sto. will evetually be, ad evaluatig ->value i the coditio will crash.! So let s make the loo sto if becomes. ListNode *=; ull // oits to what oits to while (!= && ->value!=5.6) { = ->ext; //makes oit to the ext ode!17 T7:Fid a ode AND it s revious eighbor.! sometimes we eed to track the curret ad the revious ode: ListNode * = ; //curret ode, set to first ode ListNode * = ; //revious ode, oe yet while (!= && ->value!=5.6) { = ; //save curret ode address = ->ext; //advace curret ode to ext oe ull!18 T8:Aed to the ed of a o-emty list! Create a ew ode, ad fid the last ode: T9:Delete the first ode of a o-emty list ull ListNode *ewnode = ew ListNode; ewnode->value = 3.3; ewnode->ext = ; ListNode *=; while (->ext!=) { = ->ext; We ve doe this already. ewnode 3.3 ull! delete the first elemet of a o-emty list = ->ext;! what about deallocatig the first ode? Oos. ListNode * = ; = ->ext; delete ;! Now make the last ode s ext oit to ewnode. ->ext = ewnode;!19!20

6 T10: Delete a elemet, give ad T11:Isert a ew elemet, give ad Deletig 13 from the list ->ext = ->ext; ad must ot be ull Isertig 17 ito the list ewnode 17 must ot be ull ->ext = ewnode; ewnode->ext = ; delete ; !21 ewnode!22 Exercise: fid four errors 18.2 List oeratios! it mai() { struct ode { it data; ode * ext; // create emty list ode * list; // isert six odes at frot of list ode *; for (it i=0;i<=5;i++) { = ew ode; ->data = i; ->ext = list;! Some basic oeratios over a list: - create a ew, emty list - aed a value to the ed of the list - isert a value withi the list - delete a value (remove it from the list) - dislay the values i the list // rit list = list; while (!) { cout << ->data << " "; = ->ext; cout << edl;!23 - delete/destroy the list (if it was dyamically allocated)!24

7 Declarig the List data tye NumberList class declaratio NumberList.h! We will be defiig a class called NumberList to rereset a List data tye. - ours will store values of tye double, usig a liked list.! The class will imlemet the basic oeratios over lists o the revious slide.! I the rivate sectio of the class we will: - defie a struct data tye for the odes - defie a oiter variable () that oits to the first ode i the list.!25! class NumberList { rivate: struct ListNode // the ode data tye { double value; // data ListNode *ext; // tr to ext ode ; ListNode *; // the list ; ublic: NumberList(); ~NumberList(); void aednode(double); void isertnode(double); void deletenode(double); void dislaylist(); // creates a emty list!26 Oeratio: Create the emty list Oeratio: aed ode to ed of list! Costructor: sets u emty list (This is T1, create a emty list). #iclude "NumberList.h" NumberList::NumberList() { = ; NumberList.c! aednode: adds ew ode to ed of list! Algorithm: Create a ew ode (T2) If the list is emty, Make oit to the ew ode. (T3) Else (T8) Fid the last ode i the list Make the last ode oit to the ew ode!27!28

8 void NumberList::aedNode(double um) { // Create a ew ode ad store the data i it (T2) ListNode *ewnode = ew ListNode; ewnode->value = um; ewnode->ext = ; // If emty, make oit to ew ode (T3) if (==) = ewnode; else { // Aed to ed of o-emty list (T8) ListNode * = ; // oits to first elemet // traverse list to fid last ode while (->ext) //it s ot last = ->ext; //make it t to ext // ow ts to last ode // make last ode oit to ewnode ->ext = ewnode; i NumberList.c!29 Driver to demo NumberList! ListDriver.c versio 1 (o outut) #iclude "NumberList.h" it mai() { // Defie the list NumberList list; // Aed some values to the list list.aednode(2.5); list.aednode(7.9); list.aednode(12.6); ListDriver.c!30 Traversig a Liked List Oeratio: dislay the list! Visit each ode i a liked list, to - dislay cotets, sum data, test data, etc.! Basic rocess (this is T4): set a oiter to oit to what oits to while the oiter is ot rocess data of curret ode go to the ext ode by settig the oiter to the ext field of the curret ode ed while!31 void NumberList::dislayList() { ListNode * = ; //start at the of the list // while ts to somethig (ot ), cotiue while () { //Dislay the value i the curret ode cout << ->value << ; //Move to the ext ode = ->ext; cout << edl; i NumberList.c!32

9 Driver to demo NumberList Oeratio: destroy a List! ListDriver.c versio 2 #iclude "NumberList.h" it mai() { ListDriver.c! The destructor must delete (deallocate) all odes used i the list! To do this, use list traversal to visit each ode! ~NumberList: what s wrog with this defiitio? // Defie the list NumberList list; NumberList::~NumberList() { // Aed some values to the list list.aednode(2.5); list.aednode(7.9); list.aednode(12.6); // Dislay the values i the list. list.dislaylist(); Outut: !33 ListNode *; // traversal tr = ; //start at of list while () { delete ; // delete curret = ->ext; // advace tr!34 destructor! You eed to save ->ext before deletig : NumberList::~NumberList() { ListNode *; // traversal tr i NumberList.c ListNode *; // saves the ext ode = ; //start at of list while () { = ->ext; // save the ext delete ; // delete curret = ; // advace tr!35 Oeratio: delete a ode from the list! deletenode: removes ode from list, ad deletes (deallocates) the removed ode.! This is T7 ad T10: - T7: Fid a ode AND it s revious eighbor (&) - the do T10: Delete a elemet, give ad Deletig 13 from the list!36

10 deletenode: what if or are ull?! If is ull, there is othig to delete:! If is ull, we eed to delete the first ode (T9):! Delete, accoutig for or beig ull: if (!==) { if (==) // delete the first ode = ->ext; else // ad are ot ->ext = ->ext; delete ; // sice was t, deallocate!37 //there is o else, if was, othig to remove deletenode code void NumberList::deleteNode(double um) { ListNode * = ; ListNode *; // to traverse the list // trailig ode oiter // ski odes ot equal to um, sto at last while ( && ->value!=um) { = ; // save it! = ->ext; // advace it i NumberList.c // ot ull: um was foud, set liks + delete if () { if (==) { // oits to the first elem. = ->ext; delete ; else { // oits to the redecessor ->ext = ->ext; delete ;!38 Driver to demo NumberList // set u the list NumberList list; list.aednode(2.5); list.aednode(7.9); list.aednode(12.6); list.dislaylist(); cout << edl << "remove 7.9:" << edl; list.deletenode(7.9); list.dislaylist(); cout << edl << "remove 8.9: " << edl; list.deletenode(8.9); list.dislaylist(); cout << edl << "remove 2.5: " << edl; list.deletenode(2.5); list.dislaylist(); i ListDriver.c Outut: remove 7.9: remove 8.9: remove 2.5: 12.6!39 Oeratio: isert a ode ito a liked list! Iserts a ew ode ito the middle of a list.! This is T7 ad T11: - T7: Fid a ode AND it s revious eighbor (&) we will make oit to the first elemet > 17 - the do T11: Isert a ew elemet, give ad ->ext = ewnode; ewnode->ext = ; 17!40 ewnode

11 cout << Name << ame1 << edl; isertnode: what if or are ull?! If is ull, it aeds to ed: ->ext = ewnode; ewnode->ext = ;! If is ull, we eed to add ode to frot (T3):! Isert, accoutig for beig ull: if (==) { // must be oitig to first ode = ewnode; ewnode->ext = ; else { // is ot ->ext = ewnode; ewnode->ext = ;!41 //if is ull, is oitig to the last ode, ad it works. Isertio Poit! Note that i the isertnode imlemetatio that follows, the isertio oit is immediately before the first ode i the list that has a value greater tha the value beig iserted.! This works very icely if the list is already sorted ad you wat to maitai the sort order.! Aother way to secify the isertio oit is to secify the ositio where the value should be iserted.! A third way to secify the isertio oit is to secify which elemet i the list the ew value!42 should be iserted before (or after). isertnode code void NumberList::isertNode(double um) { i NumberList.c ListNode *ewnode; // tr to ew ode ListNode *; // tr to traverse list ListNode *; // ode revious to //allocate ew ode ewnode = ew ListNode; ewnode->value = um; // ski all odes less tha um = ; while ( && ->value < um) { = ; // save = ->ext; // advace if ( == ) { = ewnode; ewnode->ext = ; else { ->ext = ewnode; ewnode->ext = ; //isert before first //isert after!43 Driver to demo NumberList it mai() { i ListDriver.c // set u the list NumberList list; list.aednode(2.5); list.aednode(7.9); list.aednode(12.6); list.dislaylist(); list.isertnode (8.5); list.dislaylist(); list.isertnode (1.5); list.dislaylist(); list.isertnode (21.5); list.dislaylist(); Outut: !44