Implement doubly linked list

JavaScript/doubly_classbased.js

@@ -0,0 +1,167 @@
+'use strict';
+
+
+class Node {
+
+  constructor(data, prev, next) {
+    this.data = data;
+    this.prev = prev || null;
+    this.next = next || null;
+  }
+
+  toString() {
+    let repr = this.data;
+    if (this.next) {
+      repr += ' -> ' + this.next.toString();
+    }
+    return repr;
+  }
+}
+
+
+class LinkedList {
+
+  constructor() {
+    this.head = null;
+    this.tail = null;
+    this.length = 0;
+  }
+
+  toString() {
+    if (!this.head) return;
+    return this.head.toString();
+  }
+
+  print() {
+    console.log(this.toString());
+  }
+
+  isEmpty() {
+    return !!this.length;
+  }
+
+
+  push(data) {
+    if (this.length === 0) {
+      this.head = new Node(data);
+      this.tail = this.head;
+    } else {
+      this.tail.next = new Node(data, this.tail);
+      this.tail = this.tail.next;
+    }
+    this.length += 1;
+    return this;
+  }
+
+  pop() {
+    if (!this.tail) {
+      return;
+    }
+
+    let data = this.tail.data;
+    this.tail = this.tail.prev;
+    this.tail.next = null;
+    this.length -= 1;
+    return data;
+  }
+
+  findFirst(data) {
+    let current = this.head;
+    while (current) {
+      if (current.data === data) {
+        return current;
+      }
+      current = current.next;
+    }
+    return null;
+  }
+
+  findAll(data) {
+    let current = this.head;
+    let nodes = [];
+    while (current) {
+      if (current.data === data) {
+        nodes.push(current);
+      }
+      current = current.next;
+    }
+    return nodes;
+  }
+
+  find(data, callback) {
+    let current = this.head;
+    while (current) {
+      if (current.data === data) {
+        callback(current);
+      }
+      current = current.next;
+    }
+  }
+
+  findReg(regex) {
+    let current = this.head;
+    let nodes = [];
+    while (current) {
+      if (current.data.toString().match(regex)) {
+        nodes.push(current);
+      }
+      current = current.next;
+    }
+    return nodes;
+  }
+
+  map(func) {
+    let current = this.head;
+    while (current) {
+      current.data = func(current.data);
+      current = current.next;
+    }
+    return this;
+  }
+
+  filter(func) {
+    let filtered = new LinkedList();
+    let current = this.head;
+    while (current) {
+      if (func(current.data)) {
+        filtered.push(current.data);
+      }
+      current = current.next;
+    }
+    return filtered;
+  }
+
+  reduce(func) {
+    let reduced = this.head.data || null;
+    let current = this.head;
+    while (current && current.next) {
+      reduced = func(reduced, current.next.data);
+      current = current.next;
+    }
+    return reduced;
+  }
+
+  flatten() {
+  /*
+  Flatten the list
+  from
+    element1 -> LinkedList(element2, LinkedList(element3)) -> element4
+  to
+    element1 -> element2 -> element3 -> element4
+  */
+    let current = this.head;
+    while (current) {
+      if (typeof(current.data) === 'LinkedList') {
+        current.data = current.data.flatten();
+        while (!current.data.isEmpty()) {
+          let temp = current.data.pop();
+          temp.prev = current.prev;
+          temp.next = current.next;
+          current.prev.next = current.next.prev = temp;
+        }
+      }
+      current = current.next;
+    }
+    return this;
+  }
+}