feat: insertion sort with binary search (TheAlgorithms#1182)

syedjafer_k · web-flow · commit 18baef8e7e5b · 2022-10-16T10:47:18.000+02:00
diff --git a/Sorts/BinaryInsertionSort.js b/Sorts/BinaryInsertionSort.js
@@ -0,0 +1,60 @@
+/**
+ * Pure Implementation of Binary Search Algorithm
+ *
+ * Binary insertion sort is a sorting algorithm similar to insertion sort,
+ * but instead of using linear search to find the position
+ * where the element should be inserted, we use binary search.
+ * Thus, we reduce the number of comparisons for inserting one element from O(N)
+ * (Time complexity in Insertion Sort) to O(log N).
+ *
+ */
+
+/**
+ * Search the key element in the array from start position to end position.
+ *
+ * @param {Array} array Array of numbers.
+ * @param {Number} key Value to be searched
+ * @param {Number} start start index position of array
+ * @param {Number} end end index position of array
+ * @return {Number} Position of the key element
+ */
+function binarySearch (array, key, start, end) {
+  if (start === end) {
+    if (array[start] > key) {
+      return start
+    } else {
+      return start + 1
+    }
+  }
+
+  if (start > end) {
+    return start
+  }
+
+  const mid = Math.floor((start + end) / 2)
+
+  if (array[mid] < key) {
+    return binarySearch(array, key, mid + 1, end)
+  } else if (array[mid] > key) {
+    return binarySearch(array, key, start, mid - 1)
+  } else {
+    return mid
+  }
+}
+
+/**
+ * Binary Insertion Sort
+ *
+ * @param {Array} list List to be sorted.
+ * @return {Array} The sorted list.
+ */
+export function binaryInsertionSort (array) {
+  const totalLength = array.length
+  for (let i = 1; i < totalLength; i += 1) {
+    const key = array[i]
+    const indexPosition = binarySearch(array, key, 0, i - 1)
+    array.splice(i, 1)
+    array.splice(indexPosition, 0, key)
+  }
+  return array
+}
diff --git a/Sorts/test/BinaryInsertionSort.test.js b/Sorts/test/BinaryInsertionSort.test.js
@@ -0,0 +1,8 @@
+import { binaryInsertionSort } from '../BinaryInsertionSort'
+
+describe('BinaryInsertionSort', () => {
+  it('should sort arrays correctly', () => {
+    expect(binaryInsertionSort([5, 4, 3, 2, 1])).toEqual([1, 2, 3, 4, 5])
+    expect(binaryInsertionSort([7, 9, 4, 3, 5])).toEqual([3, 4, 5, 7, 9])
+  })
+})
