TheAlgorithms · raklaptudirm · Dec 20, 2021 · Dec 9, 2021 · Dec 19, 2021 · Dec 20, 2021
@@ -8,22 +8,68 @@
  * else if the length of the array is odd number, the median value will be the middle number in the array
  */
 
-const averageMedian = (numbers) => {
-  let median = 0
-  const numLength = numbers.length
-  numbers = numbers.sort(sortNumbers)
-
-  if (numLength % 2 === 0) {
-    median = (numbers[numLength / 2 - 1] + numbers[numLength / 2]) / 2
-  } else {
-    median = numbers[(numLength - 1) / 2]
+const toArray = (_iterable, _selector) => {
+  const res = [];
+  if(!_selector) {
+    for (const x of _iterable)
+      res.push(x);
   }
+  else {
+    for (const x of _iterable)
+      res.push(_selector(x));
+  }
+  return res;
+};
 
-  return median
-}
+const averageMedian = (_arrayOrIterable, {sort, selector} = {}) => {
+  let array = _arrayOrIterable;
+
+  const isArray = Array.isArray(_arrayOrIterable);
+  if(!isArray)
+    array = toArray(array);
+
+  const len = array.length;
+  if (len <= 0)
+    return undefined;
+  if (len === 1) {
+    if (selector)
+      return selector(array[0]);
+    return array[0];
+  }
+
+  if (len === 2) {
+    const a = array[0];
+    const b = array[1];
+    if (selector)
+      return 0.5 * (selector(a) + selector(b));
+    return 0.5 * (a + b);
+  }
+
+  let data = array;
+  if (sort !== false) {
+    if(isArray)
+      data = [...array];
+
+    if (selector)
+      data.sort((_x, _y) => selector(_x) - selector(_y));
+    else
+      data.sort();
+  }
+
+  if (len % 2 === 0) {
+    const i = len / 2;
+    const a = data[i - 1];
+    const b = data[i];
+    if (selector)
+      return 0.5 * (selector(a) + selector(b));
+    return 0.5 * (a + b);
+  }
+
+  const z = data[(len - 1) >> 1];
+  if (selector)
+    return selector(z);
 
-const sortNumbers = (num1, num2) => {
-  return num1 - num2
+  return z;
 }
 
 export { averageMedian }
diff --git a/Maths/test/AverageMedian.test.js b/Maths/test/AverageMedian.test.js
@@ -1,21 +1,83 @@
 import { averageMedian } from '../AverageMedian'
 
-test('should return the median of an array of numbers:', () => {
-  const medianValue = averageMedian([1, 2, 6, 4, 5])
-  expect(medianValue).toBe(4)
-})
-
-test('should return the median of an array of numbers:', () => {
-  const medianValue = averageMedian([8, 9, 1, 2, 5, 10, 11])
-  expect(medianValue).toBe(8)
-})
-
-test('should return the median of an array of numbers:', () => {
-  const medianValue = averageMedian([15, 18, 3, 9, 13, 5])
-  expect(medianValue).toBe(11)
-})
-
-test('should return the median of an array of numbers:', () => {
-  const medianValue = averageMedian([1, 2, 3, 4, 6, 8])
-  expect(medianValue).toBe(3.5)
-})
+describe('math median tests', () => {
+  // ----------------------------------------------------------------------
+  test('given empty array then median is undefined', () => {
+    expect(averageMedian([])).toBeUndefined();
+  });
+  // ----------------------------------------------------------------------
+  test('given single array then median is found', () => {
+    expect(averageMedian([1])).toBe(1);
+  });
+  // ----------------------------------------------------------------------
+  test('given array then median not changed the origin', () => {
+    const src = [1,2,1,2,0,2];
+    averageMedian([src]);
+    expect(src).toEqual([1,2,1,2,0,2]);
+  });
+  // ----------------------------------------------------------------------
+  test('given array when selector defined then median not changed the origin', () => {
+    const src = [1,2,1,2,0,2];
+    averageMedian([src],{selector:_x=>_x});
+    expect(src).toEqual([1,2,1,2,0,2]);
+  });
+  // ----------------------------------------------------------------------
+  test('given single array when selector defined then median is found', () => {
+    expect(averageMedian(["abc"], {selector: _x => _x.length})).toBe(3);
+  });
+    // ----------------------------------------------------------------------
+    test('given sorted array then median is found', () => {
+      expect(averageMedian([1],{sort:false})).toBe(1);
+      expect(averageMedian([1,2],{sort:false})).toBe(1.5);
+      expect(averageMedian([1,2,5],{sort:false})).toBe(2);
+      expect(averageMedian([1,2,5,5],{sort:false})).toBe(3.5);
+      expect(averageMedian([1,2,5,5,5],{sort:false})).toBe(5);
+    });
+    // ----------------------------------------------------------------------
+    test('given sorted array when selector defined then median is found', () => {
+      expect(averageMedian([1],{sort:false,selector:_x=>_x})).toBe(1);
+      expect(averageMedian([1,2],{sort:false,selector:_x=>_x})).toBe(1.5);
+      expect(averageMedian([1,2,5],{sort:false,selector:_x=>_x})).toBe(2);
+      expect(averageMedian([1,2,5,5],{sort:false,selector:_x=>_x})).toBe(3.5);
+      expect(averageMedian([1,2,5,5,5],{sort:false,selector:_x=>_x})).toBe(5);
+    });
+    // ----------------------------------------------------------------------
+    test('given not sorted array then median is found', () => {
+      expect(averageMedian([1])).toBe(1);
+      expect(averageMedian([2,1])).toBe(1.5);
+      expect(averageMedian([5,1,2])).toBe(2);
+      expect(averageMedian([5,2,1,5])).toBe(3.5);
+      expect(averageMedian([5,1,5,2,5])).toBe(5);
+    });
+    // ----------------------------------------------------------------------
+    test('given not sorted array when selector defined  then median is found', () => {
+      expect(averageMedian([1],{selector:_x=>_x})).toBe(1);
+      expect(averageMedian([2,1],{selector:_x=>_x})).toBe(1.5);
+      expect(averageMedian([5,1,2],{selector:_x=>_x})).toBe(2);
+      expect(averageMedian([5,2,1,5],{selector:_x=>_x})).toBe(3.5);
+      expect(averageMedian([5,1,5,2,5],{selector:_x=>_x})).toBe(5);
+    });
+    // ----------------------------------------------------------------------
+    test('given empty generator then median is undefined', () => {
+      const src = function*(){}
+      expect(averageMedian(src())).toBeUndefined();
+    });
+    // ----------------------------------------------------------------------
+    test('given generator then median is found', () => {
+      const src = function*(){
+        yield 1;
+        yield -1;
+        yield 0;
+      }
+      expect(averageMedian(src())).toBe(0);
+    });
+    // ----------------------------------------------------------------------
+    test('given string generator then median string length is found', () => {
+      const src = function*(){
+        yield "abc";
+        yield "de";
+        yield "qwertyq";
+      }
+      expect(averageMedian(src(),{selector:_x=>_x.length})).toBe(3);
+    });
+});