Added reverse method to Singly LL (Closes #5)

Author: CoffeelessProgrammer

Data-Structures/Linked-Lists/DoublyLinkedList.ts

@@ -273,9 +273,9 @@ if (import.meta.main) {
   ATLA.removeElementAtIndex(0, true);
   ATLA.removeElementAtIndex(1, true);
   ATLA.removeElementAtIndex(0, true);
-  console.log('----------------------------------');
-
   printLinkedList(ATLA);
+  
+  console.log('----------------------------------');
   console.log();
 
   ATLA.insert('Katara', 0, true);
@@ -359,8 +359,8 @@ if (import.meta.main) {
 // Removing element at index 1: "Sokka"
 // Removing element at index 0: "Zuko"
 // Removing element at index 0: "Iroh"
-// ----------------------------------
 // Empty linked list -_-
+// ----------------------------------
 //
 // --------- Prepending Katara ---------
 // --- Node Count: 1

Data-Structures/Linked-Lists/LinkedList.ts

@@ -141,6 +141,31 @@ export default class LinkedList<T> {
     return currentNode;
   }
 
+  public reverse(): boolean {
+    if (this.length < 2 || !this.head || !this.tail) return false;
+
+    this.tail = this.head;                // Current head will become the new tail
+
+    let first = this.head;
+    let second = first.getNext();
+    let tempNode;                         // Will be the third sequential node in deletion sequence
+
+    // Travel up the tree while the second node is present, i.e. not null
+    while(second) {
+      tempNode = second.getNext();
+
+      second.setNext(first);
+
+      first = second;
+      second = tempNode;
+    }
+
+    this.tail.setNext(null);
+    this.head = first;
+
+    return true;
+  }
+
   public toString(nodesPerGroup?: number): string {
     if (this.length === 0 || !this.head) {
       return "";
@@ -214,6 +239,11 @@ if (import.meta.main) {
   printSearchFor('Zuko', ATLA);
   printGetValueAtIndex(2, ATLA);
   printGetValueAtIndex(5, ATLA);
+
+  console.log('------------ Reversing List ------------');
+  ATLA.reverse();
+  printLinkedList(ATLA);
+
   console.log('----------------------------------');
 
   printRemoveIndex(1, ATLA);
@@ -234,6 +264,10 @@ if (import.meta.main) {
   ATLA.append('Aang');
   printLinkedList(ATLA);
 
+  console.log('------------ Reversing List ------------');
+  ATLA.reverse();
+  printLinkedList(ATLA);
+
   // RUN: deno run Data-Structures/Linked-Lists/LinkedList.ts
 }
 
@@ -243,7 +277,7 @@ if (import.meta.main) {
 //  HEAD { value: "Appa", next: true }
 //          1 { value: "Sokka", next: true }
 //                  2 { value: "Katara", next: false } TAIL
-
+//
 // --- Node Count: 6
 //  HEAD { value: "Appa", next: true }
 //          1 { value: "Zuko", next: true }
@@ -259,40 +293,54 @@ if (import.meta.main) {
 // "Zuko" found at index: 1
 // Element at index 2: Sokka
 // Element at index 5: Katara
+// ------------ Reversing List ------------
+// --- Node Count: 6
+//  HEAD { value: "Katara", next: true }
+//          1 { value: "Iroh", next: true }
+//                  2 { value: "Aang", next: true }
+//                          3 { value: "Sokka", next: true }
+//                                  4 { value: "Zuko", next: true }
+//                                          5 { value: "Appa", next: false } TAIL
+//
 // ----------------------------------
-// Removing element at index 1: "Zuko"
+// Removing element at index 1: "Iroh"
 // --- Node Count: 5
-//  HEAD { value: "Appa", next: true }
-//          1 { value: "Sokka", next: true }
-//                  2 { value: "Aang", next: true }
-//                          3 { value: "Iroh", next: true }
-//                                  4 { value: "Katara", next: false } TAIL
+//  HEAD { value: "Katara", next: true }
+//          1 { value: "Aang", next: true }
+//                  2 { value: "Sokka", next: true }
+//                          3 { value: "Zuko", next: true }
+//                                  4 { value: "Appa", next: false } TAIL
 //
-// Removing element at index 0: "Appa"
+// Removing element at index 0: "Katara"
 // --- Node Count: 4
-//  HEAD { value: "Sokka", next: true }
-//          1 { value: "Aang", next: true }
-//                  2 { value: "Iroh", next: true }
-//                          3 { value: "Katara", next: false } TAIL
+//  HEAD { value: "Aang", next: true }
+//          1 { value: "Sokka", next: true }
+//                  2 { value: "Zuko", next: true }
+//                          3 { value: "Appa", next: false } TAIL
 //
-// Removing element at index 2: "Iroh"
+// Removing element at index 2: "Zuko"
 // --- Node Count: 3
-//  HEAD { value: "Sokka", next: true }
-//          1 { value: "Aang", next: true }
-//                  2 { value: "Katara", next: false } TAIL
+//  HEAD { value: "Aang", next: true }
+//          1 { value: "Sokka", next: true }
+//                  2 { value: "Appa", next: false } TAIL
 //
-// Removing element at index 2: "Katara"
+// Removing element at index 2: "Appa"
 // --- Node Count: 2
-//  HEAD { value: "Sokka", next: true }
-//          1 { value: "Aang", next: false } TAIL
+//  HEAD { value: "Aang", next: true }
+//          1 { value: "Sokka", next: false } TAIL
 //
-// Removing element at index 1: "Aang"
-// Removing element at index 0: "Sokka"
+// Removing element at index 1: "Sokka"
+// Removing element at index 0: "Aang"
 // Empty linked list -_-
 // ----------------------------------
 // --- Node Count: 1
 //  HEAD { value: "Katara", next: false } TAIL
 //
 // --- Node Count: 2
 //  HEAD { value: "Katara", next: true }
-//          1 { value: "Aang", next: false } TAIL
+//          1 { value: "Aang", next: false } TAIL
+//
+// ------------ Reversing List ------------
+// --- Node Count: 2
+//  HEAD { value: "Aang", next: true }
+//          1 { value: "Katara", next: false } TAIL

Data-Structures/Linked-Lists/SinglyNode.ts

@@ -11,7 +11,7 @@ export default class LinkedListNode<T> {
     this.value = value;
   }
 
-  public setNext(nextNode: LinkedListNode<T>) {
+  public setNext(nextNode: LinkedListNode<T> | null) {
     this.next = nextNode;
   }
 

Data-Structures/README.md

@@ -5,7 +5,7 @@
 - [X] Hash Tables
 - [X] Stacks
 - [X] Queues
-- [ ] Linked Lists
+- [X] Linked Lists
 - [X] Trees
   - [X] Binary Search Tree (BST)
     - AVL Tree
@@ -20,8 +20,11 @@
 - [Comprehensive List of Data Structures](https://en.wikipedia.org/wiki/List_of_data_structures "Wikipedia: DS List")
 - [Visualizing Data Structures & Algorithms](https://visualgo.net/en)
 
-### Trees
+### Foundations
+- [Arrays vs Linked Lists: Youtube](https://youtu.be/DyG9S9nAlUM)
 - [Linked List: VisuAlgo](https://visualgo.net/en/list)
+
+### Trees
 - [Binary Search Tree: VisuAlgo](https://visualgo.net/bn/bst?slide=1)
 - [Binary Heap: VisuAlgo](https://visualgo.net/en/heap)
 - [AVL Tree Visualization](https://www.cs.usfca.edu/~galles/visualization/AVLtree.html)

README.md

@@ -12,7 +12,7 @@
 - [X] Hash Tables
 - [X] Stacks
 - [X] Queues
-- [ ] Linked Lists
+- [X] Linked Lists
 - [X] Trees
 - [ ] Graphs