--update: addAt()

Author: ashokdey

src/_DataStructures_/LinkedList/LinkedList.test.js

@@ -175,7 +175,7 @@ describe('Data Structures: Linked Lists', () => {
         list.addAtEnd('There!');
         list.addAtEnd('Welcome');
       });
-      
+
       it('Should return `null` for empty list regardless of index value', () => {
         list.delete();
         expect(list.getAt(10)).toEqual(null);
@@ -189,5 +189,32 @@ describe('Data Structures: Linked Lists', () => {
         expect(list.getAt(10).data).toEqual('Welcome');
       });
     });
+
+    describe('addAt(index, value)', () => {
+      beforeEach(() => {
+        list.addAtBeginning('Hello');
+        list.addAtEnd('There!');
+        list.addAtEnd('Welcome');
+      });
+
+      it('Should add at the beginning of empty list', () => {
+        list.delete();
+        list.addAt(10, 'Boom');
+        expect(list.getFirst().data).toEqual('Boom');
+      });
+
+      it('Should add at the end of the list if the index is out of bound', () => {
+        list.addAtEnd(1010);
+        list.addAt(10, 'Boom');
+        expect(list.getLast().data).toEqual('Boom');
+      });
+
+      it('Should add new element at the given position', () => {
+        list.addAt(2, 'Stranger');
+        expect(list.getAt(2).data).toEqual('Stranger');
+        expect(list.getAt(1).data).toEqual('There!');
+        expect(list.getAt(0).data).toEqual('Hello');
+      });
+    });
   });
 });

src/_DataStructures_/LinkedList/index.js

@@ -84,6 +84,29 @@ class LinkedList {
     return address;
   }
 
+  addAt(index, element) {
+    if (!this.head) {
+      return this.addAtBeginning(element);
+    }
+
+    if (index >= this.length()) {
+      return this.addAtEnd(element);
+    }
+
+    let address = this.head;
+    let previous = this.head;
+    let count = index;
+
+    while (count) {
+      previous = address;
+      address = address.next;
+      count -= 1;
+    }
+
+    previous.next = new Node(element, previous.next);
+    return 0;
+  }
+
   length() {
     let address = this.head;
     let count = 0;