merge: binarySearch (#884)

* required, optional param left-to-right approch in BS

* base case return early to avoid nested if block

* codes formated with standard.js

Author: AbmSourav

Recursive/BinarySearch.js

@@ -10,27 +10,25 @@
  * @see [BinarySearch](https://en.wikipedia.org/wiki/Binary_search_algorithm)
  */
 
-const binarySearch = (arr, low = 0, high = arr.length - 1, searchValue) => {
-  if (high >= low) {
-    const mid = low + Math.floor((high - low) / 2)
+const binarySearch = (arr, searchValue, low = 0, high = arr.length - 1) => {
+  // base case
+  if (high < low || arr.length === 0) return -1
 
-    // If the element is present at the middle
-    if (arr[mid] === searchValue) {
-      return mid
-    }
+  const mid = low + Math.floor((high - low) / 2)
 
-    // If element is smaller than mid, then
-    // it can only be present in left subarray
-    if (arr[mid] > searchValue) {
-      return binarySearch(arr, low, mid - 1, searchValue)
-    }
+  // If the element is present at the middle
+  if (arr[mid] === searchValue) {
+    return mid
+  }
 
-    // Else the element can only be present in right subarray
-    return binarySearch(arr, mid + 1, high, searchValue)
+  // If element is smaller than mid, then
+  // it can only be present in left subarray
+  if (arr[mid] > searchValue) {
+    return binarySearch(arr, searchValue, low, mid - 1)
   }
 
-  // We reach here when element is not present in array
-  return -1
+  // Else the element can only be present in right subarray
+  return binarySearch(arr, searchValue, mid + 1, high)
 }
 
 export { binarySearch }

Recursive/test/BinarySearch.test.js

@@ -7,26 +7,26 @@ describe('BinarySearch', () => {
 
   it('should return index 3 for searchValue 10', () => {
     const searchValue = 10
-    expect(binarySearch(arr, low, high, searchValue)).toBe(3)
+    expect(binarySearch(arr, searchValue, low, high)).toBe(3)
   })
 
   it('should return index 0 for searchValue 2', () => {
     const searchValue = 2
-    expect(binarySearch(arr, low, high, searchValue)).toBe(0)
+    expect(binarySearch(arr, searchValue, low, high)).toBe(0)
   })
 
   it('should return index 13 for searchValue 999', () => {
     const searchValue = 999
-    expect(binarySearch(arr, low, high, searchValue)).toBe(13)
+    expect(binarySearch(arr, searchValue, low, high)).toBe(13)
   })
 
   it('should return -1 for searchValue 1', () => {
     const searchValue = 1
-    expect(binarySearch(arr, low, high, searchValue)).toBe(-1)
+    expect(binarySearch(arr, searchValue, low, high)).toBe(-1)
   })
 
   it('should return -1 for searchValue 1000', () => {
     const searchValue = 1000
-    expect(binarySearch(arr, low, high, searchValue)).toBe(-1)
+    expect(binarySearch(arr, searchValue, low, high)).toBe(-1)
   })
 })