From 0885576644f65836295f9c6d3f6f99c6e6c045cd Mon Sep 17 00:00:00 2001
From: "ravikishan.69" <ravikishan63392@gmail.com>
Date: Mon, 9 Oct 2023 11:45:51 +0530
Subject: [PATCH] Adding the Doubly Linked List and Test

---
 .../linked_list/doubly_linked_list.dart       | 356 +++++++++
 .../doubly_linked_list_test.dart              | 715 ++++++++++++++++++
 2 files changed, 1071 insertions(+)
 create mode 100644 data_structures/linked_list/doubly_linked_list.dart
 create mode 100644 tests/data_structures/doubly_linked_list_test.dart

diff --git a/data_structures/linked_list/doubly_linked_list.dart b/data_structures/linked_list/doubly_linked_list.dart
new file mode 100644
index 00000000..d73ee70b
--- /dev/null
+++ b/data_structures/linked_list/doubly_linked_list.dart
@@ -0,0 +1,356 @@
+/**
+ * Doubly Linked List
+ */
+
+/**
+ * Node class
+ */
+class Node<T> {
+  T data;
+  Node<T> next;
+  Node<T> prev;
+
+  Node(this.data, [this.next, this.prev]);
+}
+
+/**
+ * Doubly Linked List class
+ */
+class DoublyLinkedList<T> extends Iterator<T> {
+  Node<T> _head;
+  Node<T> _tail;
+  int _length = 0;
+  Node<T> _current;
+
+  DoublyLinkedList() {
+    this._head = null;
+    this._tail = null;
+    this._length = 0;
+  }
+
+  /**
+   * Push
+   */
+  void push(T data) {
+    Node<T> newNode = new Node(data);
+
+    if (this._length == 0) {
+      this._head = newNode;
+      this._tail = newNode;
+    } else {
+      this._tail.next = newNode;
+      newNode.prev = this._tail;
+      this._tail = newNode;
+    }
+
+    this._length++;
+  }
+
+  /**
+   * Pop
+   */
+  Node<T> pop() {
+    if (this._length == 0) return null;
+
+    Node<T> poppedNode = this._tail;
+
+    if (this._length == 1) {
+      this._head = null;
+      this._tail = null;
+    } else {
+      this._tail = poppedNode.prev;
+      this._tail.next = null;
+      poppedNode.prev = null;
+    }
+
+    this._length--;
+
+    return poppedNode;
+  }
+
+  /**
+   * Shift
+   */
+  Node<T> shift() {
+    if (this._length == 0) return null;
+
+    Node<T> shiftedNode = this._head;
+
+    if (this._length == 1) {
+      this._head = null;
+      this._tail = null;
+    } else {
+      this._head = shiftedNode.next;
+      this._head.prev = null;
+      shiftedNode.next = null;
+    }
+
+    this._length--;
+
+    return shiftedNode;
+  }
+
+  /**
+   * Unshift
+   */
+  void unshift(T data) {
+    Node<T> newNode = new Node(data);
+
+    if (this._length == 0) {
+      this._head = newNode;
+      this._tail = newNode;
+    } else {
+      this._head.prev = newNode;
+      newNode.next = this._head;
+      this._head = newNode;
+    }
+
+    this._length++;
+  }
+
+  /**
+   * Get
+   */
+  Node<T> get(int index) {
+    if (index < 0 || index >= this._length) return null;
+
+    Node<T> current;
+    int count;
+
+    if (index <= this._length / 2) {
+      count = 0;
+      current = this._head;
+
+      while (count != index) {
+        current = current.next;
+        count++;
+      }
+    } else {
+      count = this._length - 1;
+      current = this._tail;
+
+      while (count != index) {
+        current = current.prev;
+        count--;
+      }
+    }
+
+    return current;
+  }
+
+  /**
+   * Set
+   */
+  bool set(int index, T data) {
+    Node<T> foundNode = this.get(index);
+
+    if (foundNode != null) {
+      foundNode.data = data;
+      return true;
+    }
+
+    return false;
+  }
+
+  /**
+   * Insert
+   */
+  bool insert(int index, T data) {
+    if (index < 0 || index > this._length) return false;
+
+    if (index == 0) {
+      this.unshift(data);
+      return true;
+    }
+
+    if (index == this._length) {
+      this.push(data);
+      return true;
+    }
+
+    Node<T> newNode = new Node(data);
+    Node<T> beforeNode = this.get(index - 1);
+    Node<T> afterNode = beforeNode.next;
+
+    beforeNode.next = newNode;
+    newNode.prev = beforeNode;
+    newNode.next = afterNode;
+    afterNode.prev = newNode;
+
+    this._length++;
+
+    return true;
+  }
+
+  /**
+   * Remove
+   */
+  Node<T> remove(int index) {
+    if (index < 0 || index >= this._length) return null;
+
+    if (index == 0) return this.shift();
+
+    if (index == this._length - 1) return this.pop();
+
+    Node<T> removedNode = this.get(index);
+    Node<T> beforeNode = removedNode.prev;
+    Node<T> afterNode = removedNode.next;
+
+    beforeNode.next = afterNode;
+    afterNode.prev = beforeNode;
+    removedNode.next = null;
+    removedNode.prev = null;
+
+    this._length--;
+
+    return removedNode;
+  }
+
+  /**
+   * Reverse
+   */
+  void reverse() {
+    Node<T> temp = this._head;
+    this._head = this._tail;
+    this._tail = temp;
+
+    Node<T> next;
+    Node<T> prev = null;
+
+    for (int i = 0; i < this._length; i++) {
+      next = temp.next;
+      temp.next = prev;
+      temp.prev = next;
+      prev = temp;
+      temp = next;
+    }
+  }
+
+  /**
+   * Iterator
+   */
+  bool moveNext() {
+    if (this._current == null) {
+      this._current = this._head;
+    } else {
+      this._current = this._current.next;
+    }
+
+    return this._current != null;
+  }
+
+  T get current => this._current?.data;
+
+  /**
+   * Iterable
+   */
+  Iterator<T> get iterator => this;
+
+  /**
+   * Length
+   */
+  int get length => this._length;
+
+  /**
+   * Head
+   */
+  Node<T> get head => this._head;
+
+  /**
+   * Tail
+   */
+  Node<T> get tail => this._tail;
+
+  /**
+   * Print
+   */
+  void printList() {
+    List<T> list = [];
+
+    Node<T> currentNode = this._head;
+
+    while (currentNode != null) {
+      list.add(currentNode.data);
+      currentNode = currentNode.next;
+    }
+
+    print(list);
+  }
+
+  /**
+   * Print reverse
+   */
+  void printListReverse() {
+    List<T> list = [];
+
+    Node<T> currentNode = this._tail;
+
+    while (currentNode != null) {
+      list.add(currentNode.data);
+      currentNode = currentNode.prev;
+    }
+
+    print(list);
+  }
+
+  /**
+   * Clear
+   */
+  void clear() {
+    this._head = null;
+    this._tail = null;
+    this._length = 0;
+  }
+
+  /**
+   * Search
+   */
+  int search(T data) {
+    Node<T> currentNode = this._head;
+    int index = 0;
+
+    while (currentNode != null) {
+      if (currentNode.data == data) return index;
+
+      currentNode = currentNode.next;
+      index++;
+    }
+
+    return -1;
+  }
+
+  /**
+   * Contains
+   */
+  bool contains(T data) {
+    return this.search(data) != -1;
+  }
+
+  /**
+   * Is empty
+   */
+  bool get isEmpty => this._length == 0;
+
+  /**
+   * To List
+   */
+  List<T> toList() {
+    List<T> list = [];
+
+    Node<T> currentNode = this._head;
+
+    while (currentNode != null) {
+      list.add(currentNode.data);
+      currentNode = currentNode.next;
+    }
+
+    return list;
+  }
+
+  /**
+   * To String
+   */
+  String toString() {
+    return this.toList().toString();
+  }
+}
diff --git a/tests/data_structures/doubly_linked_list_test.dart b/tests/data_structures/doubly_linked_list_test.dart
new file mode 100644
index 00000000..eb57077a
--- /dev/null
+++ b/tests/data_structures/doubly_linked_list_test.dart
@@ -0,0 +1,715 @@
+import 'package:test/test.dart';
+import '../../data_structures/linked_list/doubly_linked_list.dart';
+
+class CustomClass {
+  int value;
+
+  CustomClass(this.value);
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is CustomClass &&
+          runtimeType == other.runtimeType &&
+          value == other.value;
+
+  String toString() {
+    return this.value.toString();
+  }
+}
+
+void main() {
+  group("Doubly Linked List Tests", () {
+    test("Push", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+
+      expect(list.length, 1);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 1);
+
+      list.push(2);
+
+      expect(list.length, 2);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 2);
+
+      list.push(3);
+
+      expect(list.length, 3);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 3);
+    });
+
+    test("Pop", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+
+      expect(list.length, 3);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 3);
+
+      Node poppedNode = list.pop();
+
+      expect(list.length, 2);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 2);
+      expect(poppedNode.data, 3);
+
+      poppedNode = list.pop();
+
+      expect(list.length, 1);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 1);
+      expect(poppedNode.data, 2);
+
+      poppedNode = list.pop();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(poppedNode.data, 1);
+
+      poppedNode = list.pop();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(poppedNode, null);
+    });
+
+    test("Shift", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+
+      expect(list.length, 3);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 3);
+
+      Node shiftedNode = list.shift();
+
+      expect(list.length, 2);
+      expect(list.head.data, 2);
+      expect(list.tail.data, 3);
+      expect(shiftedNode.data, 1);
+
+      shiftedNode = list.shift();
+
+      expect(list.length, 1);
+      expect(list.head.data, 3);
+      expect(list.tail.data, 3);
+      expect(shiftedNode.data, 2);
+
+      shiftedNode = list.shift();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(shiftedNode.data, 3);
+
+      shiftedNode = list.shift();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(shiftedNode, null);
+    });
+
+    test("Unshift", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.unshift(1);
+
+      expect(list.length, 1);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 1);
+
+      list.unshift(2);
+
+      expect(list.length, 2);
+      expect(list.head.data, 2);
+      expect(list.tail.data, 1);
+
+      list.unshift(3);
+
+      expect(list.length, 3);
+      expect(list.head.data, 3);
+      expect(list.tail.data, 1);
+    });
+
+    test("Get", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+
+      expect(list.length, 3);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 3);
+
+      Node node = list.get(0);
+
+      expect(node.data, 1);
+
+      node = list.get(1);
+
+      expect(node.data, 2);
+
+      node = list.get(2);
+
+      expect(node.data, 3);
+
+      node = list.get(3);
+
+      expect(node, null);
+
+      node = list.get(-1);
+
+      expect(node, null);
+    });
+
+    test("Set", () {
+      bool result;
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+
+      expect(list.length, 3);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 3);
+
+      result = list.set(0, 4);
+      expect(result, true);
+      expect(list.head.data, 4);
+
+      result = list.set(1, 5);
+      expect(result, true);
+      expect(list.head.next.data, 5);
+
+      result = list.set(2, 6);
+      expect(result, true);
+      expect(list.tail.data, 6);
+    });
+
+    test("Insert", () {
+      bool result;
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      result = list.insert(0, 1);
+      expect(result, true);
+      expect(list.length, 1);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 1);
+
+      result = list.insert(1, 2);
+      expect(result, true);
+      expect(list.length, 2);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 2);
+
+      result = list.insert(1, 3);
+      expect(result, true);
+      expect(list.length, 3);
+      expect(list.head.data, 1);
+      expect(list.head.next.data, 3);
+
+      result = list.insert(3, 4);
+      expect(result, true);
+      expect(list.length, 4);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 4);
+
+      result = list.insert(5, 5);
+      expect(result, false);
+      expect(list.length, 4);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 4);
+
+      result = list.insert(-1, 6);
+      expect(result, false);
+      expect(list.length, 4);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 4);
+
+      result = list.insert(0, 7);
+      expect(result, true);
+      expect(list.length, 5);
+      expect(list.head.data, 7);
+      expect(list.tail.data, 4);
+    });
+
+    test("Remove", () {
+      Node removedNode;
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      removedNode = list.remove(0);
+      expect(removedNode, null);
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+      removedNode = list.remove(0);
+      expect(removedNode.data, 1);
+      expect(list.length, 3);
+      expect(list.head.data, 2);
+      expect(list.tail.data, 4);
+
+      list.push(1);
+      removedNode = list.remove(2);
+      expect(removedNode.data, 4);
+      expect(list.length, 3);
+      expect(list.head.data, 2);
+      expect(list.tail.data, 1);
+
+      removedNode = list.remove(1);
+      expect(removedNode.data, 3);
+      expect(list.length, 2);
+      expect(list.head.data, 2);
+      expect(list.tail.data, 1);
+
+      removedNode = list.remove(1);
+      expect(removedNode.data, 1);
+      expect(list.length, 1);
+      expect(list.head.data, 2);
+      expect(list.tail.data, 2);
+
+      removedNode = list.remove(0);
+      expect(removedNode.data, 2);
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+    });
+
+    test("Reverse", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.length, 4);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 4);
+
+      list.reverse();
+
+      expect(list.length, 4);
+      expect(list.head.data, 4);
+      expect(list.tail.data, 1);
+    });
+
+    test("Iterator", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(list.current, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.length, 4);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 4);
+      expect(list.current, null);
+
+      list.moveNext();
+
+      expect(list.current, 1);
+
+      list.moveNext();
+
+      expect(list.current, 2);
+
+      list.moveNext();
+
+      expect(list.current, 3);
+
+      list.moveNext();
+
+      expect(list.current, 4);
+
+      list.moveNext();
+
+      expect(list.current, null);
+    });
+
+    test("Length", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.length, 4);
+
+      list.pop();
+
+      expect(list.length, 3);
+
+      list.shift();
+
+      expect(list.length, 2);
+
+      list.unshift(1);
+
+      expect(list.length, 3);
+
+      list.insert(1, 2);
+
+      expect(list.length, 4);
+
+      list.remove(1);
+
+      expect(list.length, 3);
+
+      list.reverse();
+
+      expect(list.length, 3);
+    });
+
+    test("Head", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.head, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.head.data, 1);
+
+      list.pop();
+
+      expect(list.head.data, 1);
+
+      list.shift();
+
+      expect(list.head.data, 2);
+
+      list.unshift(1);
+
+      expect(list.head.data, 1);
+
+      list.insert(1, 2);
+
+      expect(list.head.data, 1);
+
+      list.remove(1);
+
+      expect(list.head.data, 1);
+
+      list.reverse();
+
+      expect(list.head.data, 3);
+    });
+
+    test("Tail", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.tail.data, 4);
+
+      list.pop();
+
+      expect(list.tail.data, 3);
+
+      list.shift();
+
+      expect(list.tail.data, 3);
+
+      list.unshift(1);
+
+      expect(list.tail.data, 3);
+
+      list.insert(1, 2);
+
+      expect(list.tail.data, 3);
+
+      list.remove(1);
+
+      expect(list.tail.data, 3);
+
+      list.reverse();
+
+      expect(list.tail.data, 1);
+    });
+
+    test("Clear", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.length, 4);
+      expect(list.head.data, 1);
+      expect(list.tail.data, 4);
+
+      list.clear();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+    });
+
+    test("Search", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.search(1), -1);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.search(1), 0);
+      expect(list.search(2), 1);
+      expect(list.search(3), 2);
+      expect(list.search(4), 3);
+      expect(list.search(5), -1);
+    });
+
+    test("Contains", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.contains(1), false);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.contains(1), true);
+      expect(list.contains(2), true);
+      expect(list.contains(3), true);
+      expect(list.contains(4), true);
+      expect(list.contains(5), false);
+    });
+
+    test("IsEmpty", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.isEmpty, true);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.isEmpty, false);
+    });
+
+    test("ToList", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.toList(), []);
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.toList(), [1, 2, 3, 4]);
+    });
+
+    test("ToString", () {
+      DoublyLinkedList<double> list = new DoublyLinkedList();
+
+      expect(list.toString(), "[]");
+
+      list.push(1);
+      list.push(2);
+      list.push(3);
+      list.push(4);
+
+      expect(list.toString(), "[1.0, 2.0, 3.0, 4.0]");
+    });
+
+    test("Different Data Type - String", () {
+      DoublyLinkedList<String> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(list.current, null);
+
+      list.push("1");
+      list.push("2");
+      list.push("3");
+      list.push("4");
+
+      expect(list.length, 4);
+      expect(list.head.data, "1");
+      expect(list.tail.data, "4");
+      expect(list.current, null);
+
+      list.moveNext();
+
+      expect(list.current, "1");
+
+      list.moveNext();
+
+      expect(list.current, "2");
+
+      list.moveNext();
+
+      expect(list.current, "3");
+
+      list.moveNext();
+
+      expect(list.current, "4");
+
+      list.moveNext();
+
+      expect(list.current, null);
+    });
+
+    test("Different Data Type - Object", () {
+      DoublyLinkedList<Object> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(list.current, null);
+
+      list.push(new Object());
+      list.push(new Object());
+      list.push(new Object());
+      list.push(new Object());
+
+      expect(list.length, 4);
+      expect(list.head.data, isNotNull);
+      expect(list.tail.data, isNotNull);
+      expect(list.current, null);
+
+      list.moveNext();
+
+      expect(list.current, isNotNull);
+
+      list.moveNext();
+
+      expect(list.current, isNotNull);
+
+      list.moveNext();
+
+      expect(list.current, isNotNull);
+
+      list.moveNext();
+
+      expect(list.current, isNotNull);
+
+      list.moveNext();
+
+      expect(list.current, null);
+    });
+
+    test("Different Data Type - Custom Class", () {
+      DoublyLinkedList<CustomClass> list = new DoublyLinkedList();
+
+      expect(list.length, 0);
+      expect(list.head, null);
+      expect(list.tail, null);
+      expect(list.current, null);
+
+      list.push(new CustomClass(1));
+      list.push(new CustomClass(2));
+      list.push(new CustomClass(3));
+      list.push(new CustomClass(4));
+
+      expect(list.length, 4);
+      expect(list.head.data, new CustomClass(1));
+      expect(list.tail.data, new CustomClass(4));
+      expect(list.current, null);
+
+      list.moveNext();
+
+      expect(list.current, new CustomClass(1));
+
+      list.moveNext();
+
+      expect(list.current, new CustomClass(2));
+
+      list.moveNext();
+
+      expect(list.current, new CustomClass(3));
+
+      list.moveNext();
+
+      expect(list.current, new CustomClass(4));
+
+      list.moveNext();
+
+      expect(list.current, null);
+    });
+  });
+}