Add quickSort

src/sort/quick/quickSort.spec.ts

@@ -0,0 +1,17 @@
+import quickSort from './quickSort';
+
+describe('quick sort', () => {
+  it('It should return an array sorted from lowest to highest', () => {
+    const arrayToSort = [43, 65, 44, 12, 67, 1, 9, 33, 21];
+    const expectedArray = [1, 9, 12, 21, 33, 43, 44, 65, 67];
+    expect(quickSort(arrayToSort, (a: number, b: number): boolean => (a < b)))
+      .toEqual(expectedArray);
+  });
+
+  it('It should return an array sorted from highest to lowest', () => {
+    const arrayToSort = [43, 65, 44, 12, 67, 1, 9, 33, 21];
+    const expectedArray = [67, 65, 44, 43, 33, 21, 12, 9, 1];
+    expect(quickSort(arrayToSort, (a: number, b: number): boolean => (a > b)))
+      .toEqual(expectedArray);
+  });
+});

src/sort/quick/quickSort.ts

@@ -0,0 +1,29 @@
+interface CompareFunction {
+  (a: number, b: number): boolean;
+}
+
+export default function quickSort(array: number[], compareFunction:CompareFunction): number[] {
+  if (array.length < 2) {
+    return array;
+  }
+  const pivot = array[Math.floor(Math.random() * array.length)];
+
+  const left: number[] = [];
+  const right: number[] = [];
+  const equal: number[] = [];
+
+  array.forEach((value) => {
+    if (compareFunction(value, pivot)) {
+      left.push(value);
+    } else if (!compareFunction(value, pivot)) {
+      right.push(value);
+    } else {
+      equal.push(value);
+    }
+  });
+  return [
+    ...quickSort(left, compareFunction),
+    ...equal,
+    ...quickSort(right, compareFunction),
+  ];
+}