solution

Author: amejiarosario

lab/exercises/10-mixed/even-first.js

@@ -1,14 +1,15 @@
-function evenFirst(array) {
+function sortArrayByParity(A) {
   let lo = 0;
-  let hi = 1;
-  while (hi < array.length) {
-    if (array[hi] % 2 === 0) {
-      [array[hi], array[lo]] = [array[lo], array[hi]];
+  let hi = A.length - 1;
+  while (lo < hi) {
+    if (A[lo] % 2 === 0) {
       lo++;
+    } else {
+      [A[hi], A[lo]] = [A[lo], A[hi]];
+      hi--;
     }
-    hi++;
   }
-  return array;
+  return A;
 }
 
-module.exports = evenFirst;
+module.exports = sortArrayByParity;

lab/exercises/10-mixed/even-first.spec.js

@@ -1,9 +1,20 @@
 const fn = require('./even-first');
 
 describe('Sort even first and then odd', () => {
-  it('should work', () => {
+  it('should work when start with even', () => {
+    const actual = fn([0, 1, 2]);
+    expect(actual.slice(0, 2)).toEqual(expect.arrayContaining([0, 2]));
+    expect(actual.slice(2)).toEqual(expect.arrayContaining([1]));
+  });
+
+  it('should work when start with odd', () => {
     const actual = fn([5, 4, 3, 7, 8, 3, 2]);
     expect(actual.slice(0, 3)).toEqual(expect.arrayContaining([4, 8, 2]));
     expect(actual.slice(3)).toEqual(expect.arrayContaining([5, 3, 7, 3]));
   });
+
+  it('should work with empty', () => {
+    const actual = fn([]);
+    expect(actual).toEqual([]);
+  });
 });