Add binary search

src/search/binarysearch/binarySearch.spec.ts

@@ -0,0 +1,28 @@
+import binarySearch from './binarySearch';
+
+describe('binary Search', () => {
+  it(' should return null when the array is empty', () => {
+    const arrayToSearch: number[] = [];
+    expect(binarySearch(arrayToSearch, 44)).toEqual(null);
+  });
+
+  it('should return the element passed by parameter', () => {
+    const arrayToSearch = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    expect(binarySearch(arrayToSearch, 4)).toEqual(4);
+  });
+
+  it('should return null when no found the element into the array', () => {
+    const arrayToSearch = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    expect(binarySearch(arrayToSearch, 32)).toEqual(null);
+  });
+
+  it('should return should return the element when this is in the beginning of the array', () => {
+    const arrayToSearch = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    expect(binarySearch(arrayToSearch, 1)).toEqual(1);
+  });
+
+  it('should return should return the element when this is in the end of the array', () => {
+    const arrayToSearch = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    expect(binarySearch(arrayToSearch, 16)).toEqual(16);
+  });
+});

src/search/binarysearch/binarySearch.ts

@@ -0,0 +1,18 @@
+export default function binarySearch(arr: number[],
+  val:number,
+  start = 0,
+  end = arr.length - 1):number | null {
+  const mid = Math.floor((start + end) / 2);
+
+  if (val === arr[mid]) {
+    return val;
+  }
+
+  if (start >= end) {
+    return null;
+  }
+
+  return val < arr[mid]
+    ? binarySearch(arr, val, start, mid - 1)
+    : binarySearch(arr, val, mid + 1, end);
+}