New Algorithm: Parity Outlier (#1314)

* [feat] New algorithm

* [test] Add new test for ParityOutlier.js

* [fix] Reset indentation

* [fix] Reset indentation

* [fix] Style changes

* fix: improve code efficiency and a glitch

* test: adds a new possible test case

* fix: style fix

* fix: delete redundant comments and else statements

* [fix] style fix

Maths/test/ParityOutlier.test.js

@@ -0,0 +1,30 @@
+import { parityOutlier } from '../ParityOutlier'
+
+describe('Testing parityOutlier function', () => {
+  it('should return the odd number in an array of even numbers', () => {
+    expect(parityOutlier([1, 2, 16, -8848, 5126])).toBe(1)
+  })
+
+  it('should return the even number in an array of odd numbers', () => {
+    expect(parityOutlier([177, 5, 76, 1919])).toBe(76)
+  })
+
+  it('should, if the given array has only one integer element, return the integer itself', () => {
+    expect(parityOutlier([83])).toBe(83)
+    expect(parityOutlier([54])).toBe(54)
+  })
+
+  it('should, if the given array has only an odd and an even number, return the odd outlier', () => {
+    expect(parityOutlier([1, 2])).toBe(1)
+    expect(parityOutlier([4, 3])).toBe(3)
+  })
+
+  it('should return null if the given array is empty, contains only one integer, contains non-interger elements or does not have a parity outlier', () => {
+    expect(parityOutlier([])).toBe(null)
+    expect(parityOutlier([2])).toBe(null)
+    expect(parityOutlier([2, {}, 5, 'GitHub'])).toBe(null)
+    expect(parityOutlier([1, 3, 5, 7, 9])).toBe(null)
+    expect(parityOutlier([0, 2, 4, 6, 8])).toBe(null)
+    expect(parityOutlier([1, 3, 5, 7, 2, 4, 6, 8])).toBe(null)
+  })
+})