Gale-Shapley Implemented in Go with JSON test/example input

Algorithms/1.7_Gale-Shapley/galeShapley.go

@@ -0,0 +1,107 @@
+package galeshapley
+
+import (
+	"strings"
+)
+
+type Person struct {
+	Name        string   `json:"name"`
+	Male        bool     `json:"male"`
+	Preferences []string `json:"preferences"`
+
+	Match *Person
+}
+
+func Alg(males, females []Person) {
+	// by having a nil EngagedTo, a person is free... inital state all
+	// people are free
+
+	// while (∃ free man m who still has a woman w to propose to)
+	for SinglesExist(males) {
+		for mi := range males {
+			if !males[mi].IsSingle() {
+				continue
+			}
+
+			fi := males[mi].GetPreferedMatch(females)
+			if females[fi].IsSingle() {
+				match(&males[mi], &females[fi])
+				continue
+			}
+
+			if females[fi].CompareToExistingMatch(&males[mi]) {
+				females[fi].BreakUp()
+				match(&males[mi], &females[fi])
+				continue
+			}
+		}
+	}
+}
+
+func (person Person) String() string {
+	str := strings.Title(person.Name)
+	if person.Match == nil {
+		str += " (single)"
+		return str
+	}
+	str += " is engaged to "
+	str += strings.Title(person.Match.Name)
+	return str
+}
+
+func (person Person) IsSingle() bool {
+	return person.Match == nil
+}
+
+func (person *Person) BreakUp() {
+	person.Match.Match = nil
+	person.Match = nil
+}
+
+// Perfers returns
+//  n > 1 if person1 a is prefered
+//  n = 0 if there is no preference
+//  n < 1 if person2 a is prefered
+func (person Person) CompareToExistingMatch(otherPerson *Person) bool {
+	otherPersonIndex := len(person.Preferences)
+	engagedToIndex := len(person.Preferences)
+
+	for i, prefName := range person.Preferences {
+		if prefName == otherPerson.Name {
+			otherPersonIndex = i
+		}
+		if prefName == person.Match.Name {
+			engagedToIndex = i
+		}
+	}
+
+	return engagedToIndex > otherPersonIndex
+}
+
+func (person *Person) GetPreferedMatch(people []Person) int {
+	preferenceIndex := 0
+
+	for preferenceIndex = range people {
+		if people[preferenceIndex].Name == person.Preferences[0] {
+			break
+		}
+	}
+
+	if len(person.Preferences) > 1 {
+		person.Preferences = person.Preferences[1:] // shortens preference list
+	}
+	return preferenceIndex
+}
+
+func SinglesExist(people []Person) bool {
+	for i := range people {
+		if people[i].Match == nil {
+			return true
+		}
+	}
+	return false
+}
+
+func match(person1, person2 *Person) {
+	person1.Match, person2.Match = person2, person1
+}

Algorithms/1.7_Gale-Shapley/galeShapley_test.go

@@ -0,0 +1,72 @@
+package galeshapley
+
+import (
+	"testing"
+)
+
+func TestAlg00(t *testing.T) {
+	males, females, err := LoadPeopleFromFile("testdata/people00.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	Alg(males, females)
+
+	if SinglesExist(males) || SinglesExist(females) {
+		t.Fail()
+	}
+	// for _, person := range males {
+	// 	t.Log(person)
+	// }
+}
+
+func TestAlg01(t *testing.T) {
+	males, females, err := LoadPeopleFromFile("testdata/people01.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	Alg(males, females)
+
+	if SinglesExist(males) || SinglesExist(females) {
+		t.Fail()
+	}
+	// for _, person := range males {
+	// 	t.Log(person)
+	// }
+}
+
+func TestAlg02(t *testing.T) {
+	males, females, err := LoadPeopleFromFile("testdata/people02.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, person := range append(males, females...) {
+		t.Log(person)
+	}
+
+	Alg(males, females)
+
+	if SinglesExist(males) || SinglesExist(females) {
+		t.Fail()
+	}
+	for _, person := range males {
+		t.Log(person)
+	}
+}
+
+func TestLoadPeopleFromFile(t *testing.T) {
+	if _, _, err := LoadPeopleFromFile("testdata/badData.json"); err == nil {
+		t.Error("testdata/badData.json should err")
+	}
+	if _, _, err := LoadPeopleFromFile("testdata/badData00.json"); err == nil {
+		t.Error("testdata/badData00.json should err")
+	}
+	if _, _, err := LoadPeopleFromFile("testdata/badData01.json"); err == nil {
+		t.Error("testdata/badData01.json should err")
+	}
+	if _, _, err := LoadPeopleFromFile("testdata/badData02.json"); err == nil {
+		t.Error("testdata/badData02.json should err")
+	}
+}

Algorithms/1.7_Gale-Shapley/people.go

@@ -0,0 +1,52 @@
+package galeshapley
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+func LoadPeopleFromFile(filename string) ([]Person, []Person, error) {
+	file := struct {
+		People []Person `json:"people"`
+	}{}
+
+	var (
+		males, females []Person
+	)
+
+	f, err := os.Open(filename)
+	if err != nil {
+		return males, females, err
+	}
+
+	err = json.NewDecoder(f).Decode(&file)
+	if err != nil {
+		return males, females, err
+	}
+
+	for personIndex, person := range file.People {
+	nextPreference:
+		for preferenceIndex, preference := range person.Preferences {
+			if person.Name == preference {
+				return males, females, fmt.Errorf("person %s cannot prefer themeselves (preferences: %d)", person.Name, preferenceIndex)
+			}
+
+			for i, p := range file.People {
+				if i != personIndex && p.Name == preference {
+					continue nextPreference
+				}
+			}
+			return males, females, fmt.Errorf("%s has an unknown person named %s in their preference list", person.Name, preference)
+		}
+	}
+
+	for _, person := range file.People {
+		if person.Male {
+			males = append(males, person)
+		} else {
+			females = append(females, person)
+		}
+	}
+	return males, females, nil
+}

Algorithms/1.7_Gale-Shapley/testdata/badData00.json

@@ -0,0 +1,3 @@
+{
+  "foo": bad json
+}

Algorithms/1.7_Gale-Shapley/testdata/badData01.json

@@ -0,0 +1,22 @@
+{
+  "people": [
+    {
+      "name": "Am",
+      "male": true,
+      "preferences": ["Am", "Bf"]
+    }, {
+      "name": "Bm",
+      "male": true,
+      "preferences": ["Bf", "Af"]
+    },
+    {
+      "name": "Af",
+      "male": false,
+      "preferences": ["Am", "Bm"]
+    }, {
+      "name": "Bf",
+      "male": false,
+      "preferences": ["Bm", "Am"]
+    }
+  ]
+}

Algorithms/1.7_Gale-Shapley/testdata/badData02.json

@@ -0,0 +1,22 @@
+{
+  "people": [
+    {
+      "name": "Am",
+      "male": true,
+      "preferences": ["XX", "Bf"]
+    }, {
+      "name": "Bm",
+      "male": true,
+      "preferences": ["Bf", "Af"]
+    },
+    {
+      "name": "Af",
+      "male": false,
+      "preferences": ["Am", "Bm"]
+    }, {
+      "name": "Bf",
+      "male": false,
+      "preferences": ["Bm", "Am"]
+    }
+  ]
+}

Algorithms/1.7_Gale-Shapley/testdata/people00.json

@@ -0,0 +1,22 @@
+{
+  "people": [
+    {
+      "name": "Am",
+      "male": true,
+      "preferences": ["Af", "Bf"]
+    }, {
+      "name": "Bm",
+      "male": true,
+      "preferences": ["Bf", "Af"]
+    },
+    {
+      "name": "Af",
+      "male": false,
+      "preferences": ["Am", "Bm"]
+    }, {
+      "name": "Bf",
+      "male": false,
+      "preferences": ["Bm", "Am"]
+    }
+  ]
+}

Algorithms/1.7_Gale-Shapley/testdata/people01.json

@@ -0,0 +1,30 @@
+{
+  "people": [
+    {
+      "name": "Am",
+      "male": true,
+      "preferences": ["Af", "Bf", "Cf"]
+    }, {
+      "name": "Bm",
+      "male": true,
+      "preferences": ["Bf", "Cf", "Af"]
+    }, {
+      "name": "Cm",
+      "male": true,
+      "preferences": ["Bf", "Af", "Cf"]
+    },
+    {
+      "name": "Af",
+      "male": false,
+      "preferences": [ "Cm", "Am", "Bm"]
+    }, {
+      "name": "Bf",
+      "male": false,
+      "preferences": ["Bm",  "Cm", "Am"]
+    }, {
+      "name": "Cf",
+      "male": false,
+      "preferences": ["Bm", "Cm","Am"]
+    }
+  ]
+}

Algorithms/1.7_Gale-Shapley/testdata/people02.json

@@ -0,0 +1,45 @@
+{
+  "people": [
+    {
+      "name": "John",
+      "male": true,
+      "preferences": ["Stephanie", "Roxanne", "Jenny", "Maria", "Sarah"]
+    }, {
+      "name": "Michael",
+      "male": true,
+      "preferences": ["Stephanie", "Jenny", "Roxanne", "Maria", "Sarah"]
+    }, {
+      "name": "Matthew",
+      "male": true,
+      "preferences": ["Maria", "Stephanie", "Jenny", "Sarah", "Roxanne"]
+    }, {
+      "name": "Ryan",
+      "male": true,
+      "preferences": ["Maria", "Jenny", "Stephanie", "Sarah", "Roxanne"]
+    }, {
+      "name": "Andrew",
+      "male": true,
+      "preferences": ["Roxanne", "Maria", "Jenny", "Stephanie", "Sarah"]
+    }, {
+      "name": "Stephanie",
+      "male": false,
+      "preferences": ["Michael", "John", "Matthew", "Ryan", "Andrew"]
+    }, {
+      "name": "Roxanne",
+      "male": false,
+      "preferences": ["Michael", "John", "Matthew", "Ryan", "Andrew"]
+    }, {
+      "name": "Jenny",
+      "male": false,
+      "preferences": ["Michael", "Matthew", "John", "Ryan",  "Andrew"]
+    }, {
+      "name": "Maria",
+      "male": false,
+      "preferences": ["Michael", "Ryan", "Matthew", "John", "Andrew"]
+    }, {
+      "name": "Sarah",
+      "male": false,
+      "preferences": ["Matthew", "Michael", "Ryan", "John", "Andrew"]
+    }
+  ]
+}