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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 221 Lesson 7: Algorithm Development From Start to Finish

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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

### 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 */

• 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

5Austin David Jon Ichabod Manuel

5Anna 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

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++)

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