merge: add UnionFind.js plus tests (#814)

* Create UnionFind.js

* Create UnionFindTest.js

* add UnionFind.js plus tests

* implement PR comments

* implement PR comment

* fix codestyle

Co-authored-by: Administrator <pi@pglp.noip.me>

Search/test/UnionFind.test.js

@@ -0,0 +1,54 @@
+import { UnionFind } from '../UnionFind'
+
+const uf = new UnionFind(5)
+
+test('should expose .size():', () => {
+  const size = uf.size()
+  expect(size).toBe(5)
+})
+
+test('should do .union(num1, num2):', () => {
+  uf.union(1, 2)
+  uf.union(3, 4)
+  uf.union(0, 4)
+  expect(uf.connected(1, 2)).toBe(true)
+  expect(uf.connected(1, 2)).toBe(true)
+
+  expect(uf.connected(3, 4)).toBe(true)
+  expect(uf.connected(3, 0)).toBe(true)
+  expect(uf.connected(4, 0)).toBe(true)
+
+  expect(uf.connected(1, 3)).toBe(false)
+  expect(uf.connected(1, 4)).toBe(false)
+  expect(uf.connected(1, 0)).toBe(false)
+  expect(uf.connected(2, 3)).toBe(false)
+  expect(uf.connected(2, 4)).toBe(false)
+  expect(uf.connected(2, 0)).toBe(false)
+})
+
+test('.count(), should return the number of disparate groups:', () => {
+  expect(uf.count()).toBe(2)
+})
+
+test('should check if two components are connected, .connected(num1, num2):', () => {
+  expect(uf.connected(1, 2)).toBe(true)
+  expect(uf.connected(1, 3)).toBe(false)
+})
+
+test('should find the root of the tree in which the given element lives, .find(num):', () => {
+  expect(uf.find(1)).toBe(1)
+  expect(uf.find(2)).toBe(1)
+  expect(uf.find(3)).toBe(3)
+  expect(uf.find(4)).toBe(3)
+  expect(uf.find(0)).toBe(3)
+})
+
+test('should always change the id of the smaller tree and preserve the id of the larger one', () => {
+  uf.union(2, 3)
+  expect(uf.count()).toBe(1)
+  expect(uf.find(0)).toBe(3)
+  expect(uf.find(1)).toBe(3)
+  expect(uf.find(2)).toBe(3)
+  expect(uf.find(3)).toBe(3)
+  expect(uf.find(4)).toBe(3)
+})