CSCI-1200 Data Structures Fall 2017 Lecture 14 Problem Solving Techniques, Continued

Transcription

1 CSCI-1200 D Sucu Fll 2017 Lcu 14 Poblm Solving Tchniqu, Coninud Announcmn: T 2 Infomion T 2 will b hld Mondy, Oc. 23h fom 6-8pm. Pl u Submiy o indic if you lf-hndd o igh-hndd bfo 6pm Fidy. You ing ignmn will b pod on Submiy Fidy vning. No: W will -huffl h ing ignmn fom T 1. No mk-up will b givn xcp fo mgncy iuion, nd vn hn win xcu fom h Dn of Sudn o h Offic of Sudn Expinc will b quid. Covg: Lcu 1-14, Lb 1-7, HW 1-6. OPTIONAL: Pp 2 pg, blck & whi, 8.5x11, poi oinion.pdf of no you would lik o hv duing h xm. Thi my b digilly ppd o hndwin nd cnnd o phoogphd. Th fil my b no bigg hn 2MB. You will uplod hi fil o Submiy bfo Sundy W will pin hi nd ch i o you xm. You MAY NOT bing hdcopy of you no o h xm. Compu, cll-phon, plm pilo, clculo, PDA, muic ply, c. no pmid nd mu b und off. All udn mu bing hi Rnl phoo ID cd. Pcic poblm fom pviou vilbl on h cou wbi. Soluion o h poblm will b pod on Sundy vning. ALAC nd UPE will ho viw ion fo T 2 on Sundy Oc 22nd fom 1-3pm in CII 4034, 4040, nd T Tking Skill Look h poin vlu fo ch poblm, lloc im popoionl o h poblm poin. (Don pnd ll of you im on on poblm nd nglc oh big poin poblm). Look h iz of h nw box & h mpl oluion cod lin im fo ch poblm. If you oluion i going o k lo mo pc hn h box llow, w pobbly looking fo h oluion o impl poblm o impl oluion o h poblm. Going in o h, you hould know wh big opic will b covd on h. A you kim hough h poblm, if you cn mch up ho big opic o ch quion. Evn if you umpd bou how o olv h whol poblm, o om of h dil of h poblm, mk u you dmon you undnding of h big opic h i covd in h quion. R-d h poblm mn cfully. Mk u you didn mi nyhing. Ak quion duing h if omhing i uncl. Rviw of Lcu 13 Gnl Poblm Solving Tchniqu: 1. Gning nd Evluing Id 2. Mpping Id ino Cod 3. Ging h Dil Righ Smll xci o pcic h chniqu Poblm Solving Sgi / Chckh

2 Tody! Poblm Solving Exmpl: Quicko (& comp o Mgo) Dign Exmpl: Conwy Gm of Lif Anoh Dign Exmpl: Inv Wod Sch 14.1 Exmpl: Quicko Quicko lo h piion-xchng o i noh fficin oing lgoihm. Lik mgo, i i divid nd conqu lgoihm. Th p : 1. Pick n lmn, clld pivo, fom h y. 2. Rod h y o h ll lmn wih vlu l hn h pivo com bfo h pivo, whil ll lmn wih vlu g hn h pivo com f i (qul vlu cn go ih wy). Af hi piioning, h pivo i in i finl poiion. Thi i clld h piion opion. 3. Rcuivly pply h bov p o h ub-y of lmn wih mll vlu nd ply o h ub-y of lmn wih g vlu. // Choo "pivo" nd ng h vco. Run h locion of h // pivo, ping op & boom (hopfully i' n h hlfwy poin). in piion(vco<doubl>& d, in, in nd, in& wp) { in mid = ( + nd)/2; doubl pivo = d[mid]; void quickso(vco<doubl>& d, in, in nd) { if( < nd) { in pindx = piion(d,, nd); // f clling piion, on lmn (h "pivo") will b i finl poiion quickso(d,, pindx-1); quickso(d, pindx+1, nd); void quickso(vco<doubl>& d) { quickso(d,0,d.iz()-1); 2

3 Wh vlu hould you choo h pivo? Wh ou diffn opion? Wh i h od noion fo h unning im of hi lgoihm? Wh i h od noion fo h ddiionl mmoy u of hi lgoihm? Wh i h b c fo hi lgoihm? Wh i h wo c fo hi lgoihm? Comp h dign of Quicko nd Mgo. Wh i h m? Wh i diffn? 14.2 Dign Exmpl: Conwy Gm of Lif L dign pogm o imul Conwy Gm of Lif. Iniilly, du o im conin, w will focu on h min d ucu of ndd o olv h poblm. H i n ovviw of h Gm: W hv n infini wo-dimnionl gid of cll, which cn gow biily lg in ny dicion. W will imul h lif & dh of cll on h gid hough qunc of gnion. In ch gnion, ch cll i ih liv o dd. A h of gnion, cll h w dd in h pviou gnion bcom liv if i hd xcly 3 liv cll mong i 8 poibl nighbo in h pviou gnion. A h of gnion, cll h w liv in h pviou gnion min liv if nd only if i hd ih 2 o 3 liv cll mong i 8 poibl nighbo in h pviou gnion. Wih fw hn 2 nighbo, i di of lonlin. Wih mo hn 3 nighbo, i di of ovcowding. Impon no: ll bih & dh occu imulnouly in ll cll h of gnion. Oh bih / dh ul poibl, bu h hv povn o b vy ining blnc. Mny onlin ouc vilbl wih imulion ppl, pn, nd hioy. Fo xmpl: hp:// hp:// hp:// hp://n.wikipdi.og/wiki/conwy _Gm_of_Lif 3

4 Applying h Poblm Solving Sgi In cl w will binom bou how o wi imulion of h Gm of Lif, focuing on h pnion of h gid nd on h cul bih nd dh poc. Undnding h Rquimn W hv ldy bn woking owd undnding h quimn. Thi ffo includ plying wih mll xmpl by hnd o undnd h nu of h gm, nd pliminy oulin of h mjo iu. Ging Sd Wh h impon opion? How do w ogniz h opion o fom h flow of conol fo h min pogm? Wh d/infomion do w nd o pn? Wh will b h min chllng fo hi implmnion? Dil Nw Cl? Which STL cl will b uful? Ting T C? 4

5 14.3 Anoh Exmpl: Inv Wod Sch L flip h clic wod ch poblm nd ind c h bod h conin h pcifid wod! W ll b givn h gid dimnion nd h of wod, ch of which mu pp in h gid, in igh lin. Th wod my go fowd, bckwd, up, down, o long ny digonl. Ech gid cll will b ignd on of h 26 lowc l. W my lo b givn of wod wod h hould no pp nywh in h gid. H n xmpl: Inpu: id i i d i d In h middl bov, i n incoc oluion. Though i conin h 4 quid wod, i lo conin wo of h fobiddn wod. Th oluion on h igh i fully coc oluion. Thi picul poblm h 8 ol oluion including oion nd flcion. H noh xmpl: cho + bk + p + o + o + + cp b c p h k o o o And coupl mo puzzl: l + o + zd + old + zoo 14.4 Gning Id vocdo + mgn + cd + obin + cho + bufflo + d + ld + fun - c - co If unning im & mmoy no pimy concn, nd h poblm mll, wh i h impl gy o mk u ll oluion found. Cn you wi impl pogm h i ll poibilii? Wh vibl will conol h unning im & mmoy u of hi pogm? Wh i h od noion in m of h vibl fo unning im & mmoy u? Wh incmnl (bby p) impovmn cn b md o h niv pogm? How will h od noion b impovd? 5

6 14.5 Mpping Id o Cod Wh h ky p o olving hi poblm? How cn h p b ognizd ino funcion nd flow of conol fo h min funcion? Wh infomion do w nd o o? Wh C++ o STL d yp migh b hlpful? Wh nw cl migh w wn o implmn? 14.6 Ging h Dil Righ Wh h impl c w cn wih (o mk u h conol flow i coc)? Wh om pcific (impl) con c w hould wi o w won b upid whn w mov o bigg c? Wh h limiion of ou ppoch? A h cin c w won hndl cocly? Wh i h mximum c h cn b hndld in onbl moun of im? How cn w mu h pfomnc of ou lgoihm & implmnion? 6