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CEG 221 Lesson 7: Algorithm Development From Start to Finish. Mr. David Lippa. Overview. Algorithm Development : Stable Marriage What is the Stable Marriage Algorithm? Data Structure Development struct PersonType Function Development Populating people from a file Putting It Together
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CEG 221Lesson 7: Algorithm Development From Start to Finish Mr. David Lippa
Overview • Algorithm Development : Stable Marriage • What is the Stable Marriage Algorithm? • Data Structure Development • struct PersonType • Function Development • Populating people from a file • Putting It Together • Questions
Stable Marriage Algorithm • Assume Equal Numbers of Men & Women • One gender proposes, the other accepts/rejects proposals and can dump their current intended. • Each follow rules of engagement (ha ha) • The overall algorithm: • While there are still unengaged people, go through a round of match-making
Men (Proposer) Unengaged propose Dumped go to next on preference list Women (Proposee) Unengaged accept Engaged and … Like current better tell suitor to buzz off Like new one better dump fiancé for the new guy Stable Marriage:Rules of Engagement
Overall Algorithm // define data structures // make people // build preference lists while(someoneIsNotEngaged) { for each unengaged man { propose to next on preference list } } // display results
Define a Person // define NAME_SIZE, NUM_PPL struct PersonType{ char mName[NAME_SIZE]; struct PersonType* mpSpouse; struct PersonType* mpPreferences[NUM_PPL]; unsigned int mPreferred; int mHash;}; /* the hash value will be used in populating each person’s preference list */
Load People • We need to get their preference list from the user. • In this case, we will be using fprintf / fscanf, and instead of getting input or writing output from/to the terminal, we will be getting it from a file. • So let’s define the file
Define Persons.txt • Defined to be a list of people • Then each person and his/her preference list • Do this twice – one for men and for women
Make Persons.txt 5 Austin David Jon Ichabod Manuel 5 Anna Bertha Jamie Katherine Michelle Austin Michelle Katherine Bertha Anna Jamie David Katherine Jamie Bertha Anna Michelle Jon Jamie Anna Michelle Katherine Bertha Ichabod Jamie Anna Michelle Katherine Bertha Manuel Katherine Michelle Anna Bertha Jamie Anna David Jon Ichabod Manuel Austin Bertha Jon David Austin Manuel Ichabod Jamie Manuel Ichabod Jon Austin David Katherine David Austin Manuel Ichabod Jon Michelle Manuel Jon Ichabod Austin David
What else do we need? • Finds a person by name • If it doesn’t exist, it returns NULL • Prototype: struct PersonType* find(struct PersonType*[], char* name); • We won’t implement this function – assume that it works
Loader Pseudo Code 1) Read first line int num = how many to read Each string is a person’s name, add them to the array of structures 2) Do (1) one more time 3) For (i = 0; i < num; i++) read name find name in the list of pointers for (j = 0; j < num; j++) Read next person on preference list Find the person pointer Add person to name’s preference list 4) Do (3) one more time