Ye ALGORITHMe DIKJESTRA hamishe OPTIMAL PATH ro peydaa mikoneh vali dir be TARGET mirese... Agar "n" taa kaar dashte baashi baa O(n) be javabet miresi, bayad bebini too TRADE OFFe TIME COMPLEXITY va GOAL VALUE be kodoom samt meyl bayad bokoni... Osoolan too in TRADE OFF na baayad rumie rum bood, na zangie zangi...
In ALGORITHM be komake ye entekhaabe GREEDY javab ro peydaa mikone, yani too har ghadam behtarin gozineyi ke be nazaresh miaad var midaareh va ejraa mikoneh va hamishe ham be javabe OPTIMAL mireseh... In chizie ke baa REAL WORLD ham tatbigh daare, chon too REAL WORLD na LOOK AHEAD daari, na BACK TRACK... Va ammaa faje'e injaa shoroo mishe! Aghaaze ye LOGICAL CRASH!
Tooye DIKJESTRA too har marhale miaad kamtarin hazineh ro entekhaab mikon va mibine ke aya be komake on mitooneh baghieye masiraa ro kootah kone ya na... In kaaro ham be komake WEIGHThaayi anjaam mide ke ghablan dar aavordeh... Vali too REAL WORLD chand ta masaleh hast... Agar beshe inaaro hal kard, javabe behineh ro peydaa mikoni va be GOALet, hala harchi baashe miresi...
ALGORITHM injoorie age dorost yaadam moondeh baashe...

1- For all nodes "I","J" in "V", Calculate Weight[I][J]
2- S <- { Start }
3- For all I, D[I] <- Weight[Start][I]
4- While ( V - S ) <> NIL Do
......
5- Find "I" from "V-S" such that D[I] is minimum
......6- S <- S + I
......7- For all "J" in "V-S" Do
............8- D[J] <- Min { D[J] , D[I]+Weight[I][J] }
9- The answer is D[Goal]

ye raahe OPTIMAL kardane masale ine ke vaghti too marhaleye 5, "I = GOAL" baashe dige bikhiaale baghieye marahel mishi chon be GOALet residi...

Hala badbakhtiaa vase APPLY kardane in ALG. roo zendegi:

  • Hamoon avval va badtar az hame, ki mitoone WEIGHT[I][J] ro peyda kone, faghat mishe 2taa ro baham moghaayese kard, tarife daghighesh kheyli sakhteh... Ehtiaaj be ye zendegie kaamelan monazzam va baa hesaab ketaab daare, ke ghorboone shekle maahet, mano to nadaarim!
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  • START ro mikhaay kojaa begiri, alaan? Inam sakhte hodaayi, hamash migi bezaar folaan kaaro bokonm badesh shoroo mikonam!
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  • Chejoori mikhaay hameye STATEhaayi ke behesh miresi ro tashkhis bedi? Mitooni vase halle in moshkel az FLOYD-WARSHAL estefaade koni vali oonam ye eibaaye dige daare... Mogheyiyataa, moshkelaaye pishbini nashode, az beyn raftane ye seri az STATEhaa va ... hamashoon mitoonan baaes beshan ke to majboor shi ALG ro dobaare RUN koni...
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  • Az kojaa midooni in STATE ke behesh residi ghablan ettefaagh oftaade yaa na, shaayad kolliaatesh yeki baashe vali joziyat mitoone tayin konande baasheh...
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  • Vase entekhaabe behtarin gozineh(MINIMUM) gaahi bayad baa ehsaasaatet bejangi, be tanbalit ghalabe koni, kaaraaye nakhoshaayand anjaam bedi va hataa kaaraaye badbad(!) anjaam bedi... Debiaaa!
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  • Vaghti ke be GOAL residi, aya hanooz hadafet hamoon moondeh? In kheyli falsafie... Kaare man nist!
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  • ...

Vali baazam begam chon baa entekhaabe GREEDY va dar lahze ragham mikhore, mishe baa ye baar fekre amigh kardan, DECISION MAKING TREE ro ijaad koni va badan faghat kaaraaro be tartip anjaam bedio beri jelo... Javab mide baavar kon... Faghat ye VISIONe vasi' mikhaad az ayandeh... (baa LOOK AHEAD eshtebaah nagir)

Ziaad shod, chi kaar konam kholaasetar nemishod!

+ نوشته شده توسط کورش در شنبه 1385/04/17 و ساعت 20:45 |