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refactor: DisjointSet
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4ndrelim committed Apr 5, 2024
1 parent f5bc79f commit f30a77a
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2 changes: 1 addition & 1 deletion docs/team/profiles.md
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| Name | Description/About | Website (LinkedIn/GitHub/Personal) | Contributions |
|-----------|-------------------------------------------------------------------|------------------------------------------------------------------------------------------------------|-------------------------------------------------------------|
| Andre | Aspiring ML engineer. Developing this with wonderful ex-students. | You can find me [here](https://4ndrelim.github.io)! | Team lead |
| Andre | Aspiring ML engineer. Developing this with wonderful ex-students. | You can find me [here](https://4ndrelim.github.io) | Team lead |
| Kai Ting | Likes algorithms and a committed TA! | [Linkedin](https://www.linkedin.com/in/kai-ting-ho-425181268/) | Cool sorting and obscure trees! B-Trees, ORS.. |
| Changxian | DevOps is right up his alley! | ... | Hashing variants! BTS DevOps - configure Gradle & workflows |
| Shu Heng | Interested in ML, aspiring researcher. | No website but here's my [Linkedin](https://www.linkedin.com/in/yeoshuheng), please give me a job :< | CS Fundamentals! Stacks and queues! RB-tree. |
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/**
* Implementation of quick-find structure; Turns a list of objects into a data structure that supports union operations
* Note DS structure is not suited with duplicate elements!
*
* @param <T> generic type of object to be stored
*/
Expand All @@ -33,6 +34,19 @@ public DisjointSet(List<T> objects) {
}
}

/**
* Constructor to initialize Disjoint Set with a known array of objects.
* @param objects
*/
public DisjointSet(T[] objects) {
identifier = new HashMap<>();
int size = objects.length;
for (int i = 0; i < size; i++) {
// internally, component identity is tracked with integers
identifier.put(objects[i], identifier.size()); // each obj initialize with a unique identity using size;
}
}

public int size() {
return identifier.size();
}
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* Turns a list of objects into a data structure that supports union operations.
* <p>
* Note that implementation below includes path compression. Refer to README for more details
* Note DS structure is not suited with duplicate elements!
*
* @param <T> generic type of object to be stored
*/
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}
}

/**
* Constructor to initialize Disjoint Set structure with a known array of objects.
* @param objects
*/
public DisjointSet(T[] objects) {
parents = new HashMap<>();
size = new HashMap<>();
for (int i = 0; i < objects.length; i++) {
T obj = objects[i];
parents.put(obj, obj); // initially, every object forms a tree, with itself as the root
size.put(obj, 1); // each tree has size 1 at the start
}
}

/**
* Internal helper method to find the root (identifier) of an object. Note that path compression has been included.
* A point of concern might be performing path compression would require updating the sizes tracked by each node
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Expand Up @@ -24,6 +24,16 @@ public void construct_shouldCorrectlyInitializeNonEmpty() {
Assert.assertFalse(ds.find("andre", "kai ting"));
}

@Test
public void construct_shouldCorrectlyInitializeNonEmptyArray() {
String[] lst = new String[] { "andre", "chang xian", "jun neng", "kai ting", "shu heng" };

DisjointSet<String> ds = new DisjointSet<>(lst);
Assert.assertEquals(ds.size(), 5);

Assert.assertFalse(ds.find("andre", "kai ting"));
}

@Test
public void find_shouldCorrectlyFindItself() {
List<String> lst = Arrays.asList("andre", "chang xian", "jun neng");
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Expand Up @@ -24,6 +24,16 @@ public void construct_shouldCorrectlyInitializeNonEmpty() {
Assert.assertFalse(ds.find("andre", "kai ting"));
}

@Test
public void construct_shouldCorrectlyInitializeNonEmptyArray() {
String[] lst = new String[] { "andre", "chang xian", "jun neng", "kai ting", "shu heng" };

DisjointSet<String> ds = new DisjointSet<>(lst);
Assert.assertEquals(ds.size(), 5);

Assert.assertFalse(ds.find("andre", "kai ting"));
}

@Test
public void find_shouldCorrectlyFindItself() {
List<String> lst = Arrays.asList("andre", "chang xian", "jun neng");
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