merge: Create findRelativeMaximumPointCount.js (TheAlgorithms#771)

jhonDoe15 · raklaptudirm · web-flow · commit 9ad93c7b2810 · 2021-10-28T12:15:01.000+05:30
* Create find_relative_maximum_point_count.js

print number of relative maximum points in array
runs in O(n)

* rename file to match requested casing

* add inline comments and greater documentation

* fix wrong reference to algorithm explanation

* remove live code and fix function misnaming

* add multiple cases tests

* add last line as empty line

* git pull

* style changes

* move tests to test folder

* chore: fix spelling

* fix package-lock

* revert to old lock file

* chore: add line feed

Co-authored-by: Rak Laptudirm &lt;raklaptudirm@gmail.com&gt;
diff --git a/Data-Structures/Array/NumberOfLocalMaximumPoints.js b/Data-Structures/Array/NumberOfLocalMaximumPoints.js
@@ -0,0 +1,42 @@
+/**
+ * [NumberOfLocalMaximumPoints](https://www.geeksforgeeks.org/find-indices-of-all-local-maxima-and-local-minima-in-an-array/) is an algorithm to find relative bigger numbers compared to their neighbors
+ *
+ * Notes:
+ * - like the other similar local maxima search function find relative maxima points in array but doesnt stop at one but returns total point count
+ * - runs on array A of size n and returns the local maxima count using divide and conquer methodology
+ *
+ * @complexity: O(n) (on average )
+ * @complexity: O(n) (worst case)
+ * @flow
+ */
+
+// check if returned index is a local maxima
+const IsMaximumPoint = (array, index) => {
+  // handle array bounds
+  // array start
+  if (index === 0) {
+    return array[index] > array[index + 1]
+    // array end
+  } else if (index === array.length - 1) {
+    return array[index] > array[index - 1]
+    // handle index inside array bounds
+  } else {
+    return array[index] > array[index + 1] && array[index] > array[index - 1]
+  }
+}
+
+const CountLocalMaximumPoints = (array, startIndex, endIndex) => {
+  // stop check in divide and conquer recursion
+  if (startIndex === endIndex) {
+    return IsMaximumPoint(array, startIndex) ? 1 : 0
+  }
+
+  // handle the two halves
+  const middleIndex = parseInt((startIndex + endIndex) / 2)
+  return CountLocalMaximumPoints(array, startIndex, middleIndex) +
+    CountLocalMaximumPoints(array, middleIndex + 1, endIndex)
+}
+
+const NumberOfLocalMaximumPoints = (A) => CountLocalMaximumPoints(A, 0, A.length - 1)
+
+export { NumberOfLocalMaximumPoints }
diff --git a/Data-Structures/Array/test/NumberOfLocalMaximumPoints.test.js b/Data-Structures/Array/test/NumberOfLocalMaximumPoints.test.js
@@ -0,0 +1,43 @@
+import { NumberOfLocalMaximumPoints } from '../NumberOfLocalMaximumPoints'
+
+describe('LocalMaximomPoint tests', () => {
+  it('test boundry maximom points - last element', () => {
+    const Array = [1, 2, 3, 4, 5, 6, 12]
+    expect(NumberOfLocalMaximumPoints(Array)).toEqual(1)
+  })
+
+  it('test boundry maximom points - first element', () => {
+    const Array = [13, 6, 5, 4, 3, 2, 1]
+    expect(NumberOfLocalMaximumPoints(Array)).toEqual(1)
+  })
+
+  it('test boundry maximom points - both boundries have maximum points', () => {
+    // Test a mix of number types (i.e., positive/negative, numbers with decimals, fractions)
+    const Array = [13, 2, 3, 4, 5, 6, 12]
+    expect(NumberOfLocalMaximumPoints(Array)).toEqual(2)
+  })
+
+  it('multiple maximom points in the middle', () => {
+    // Test a mix of number types (i.e., positive/negative, numbers with decimals, fractions)
+    const Array = [1, 3, 2, 5, 6, 9, 2, 7, 12, 1, 0]
+    expect(NumberOfLocalMaximumPoints(Array)).toEqual(3)
+  })
+
+  it('multiple maximom points in the middle with one at end', () => {
+    // Test a mix of number types (i.e., positive/negative, numbers with decimals, fractions)
+    const Array = [1, 3, 2, 5, 6, 9, 2, 7, 12, 1, 10]
+    expect(NumberOfLocalMaximumPoints(Array)).toEqual(4)
+  })
+
+  it('multiple maximom points in the middle with one at start', () => {
+    // Test a mix of number types (i.e., positive/negative, numbers with decimals, fractions)
+    const Array = [10, 3, 2, 5, 6, 9, 2, 7, 12, 1, 0]
+    expect(NumberOfLocalMaximumPoints(Array)).toEqual(3)
+  })
+
+  it('multiple maximom points in the middle with two more at both ends', () => {
+    // Test a mix of number types (i.e., positive/negative, numbers with decimals, fractions)
+    const Array = [10, 3, 11, 5, 6, 9, 2, 7, 12, 1, 10]
+    expect(NumberOfLocalMaximumPoints(Array)).toEqual(5)
+  })
+})
