first commit

Author: Yashendra Goyal

array.js

@@ -0,0 +1,27 @@
+const myArr = [1, "Raj", [1,2], {name: "XYZ"}];
+
+// Insertion
+// Push
+myArr.push(3);
+
+console.log(myArr);
+
+// Unshift
+
+myArr.unshift([2]);
+
+// console.log(myArr);
+
+// console.log(myArr[3]);
+
+// Delete
+
+// Pop
+myArr.pop();
+
+console.log(myArr);
+
+myArr.shift();
+
+console.log(myArr);
+

doubly-linked-list/doubly-linked-list.js

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+const DoublyListNode = require("./doubly-list-node");
+
+function DoublyLinkedList() {
+    this.size = 0;
+    this.head = new DoublyListNode(0);
+    this.tail = new DoublyListNode(0);
+    this.head.next = this.tail;
+    this.tail.prev = this.head; // head ==== tail
+}
+
+// Add at index
+DoublyLinkedList.prototype.addAtIndex = function(index, value) {
+    const { size } = this;
+    if (index < 0 || index > size) {
+        return;
+    }
+
+    let prev = this.head;
+    let next = this.tail;
+
+    if (index < size - index) {
+        while (index) {
+            prev = prev.next;
+            index--;
+        }
+        next = prev.next;
+    } else {
+        while(size - index) {
+            next = next.prev;
+            index++;
+        }
+        prev = next.prev;
+    }
+
+    const newNode = new DoublyListNode(value);
+    newNode.prev = prev;
+    newNode.next = next;
+    prev.next = newNode;
+    next.prev = newNode;
+    this.size++;
+}
+
+DoublyLinkedList.prototype.addAtHead = function(value) {
+    return this.addAtIndex(0, value);
+}
+
+DoublyLinkedList.prototype.getAtIndex = function(index) {
+    const { size } = this;
+    if (index < 0 || index >= size) {
+        return null;
+    }
+
+    if (index < size - index) {
+        let node = this.head;
+        while (index >= 0) {
+            node = node.next;
+            index--;
+        }
+        return node;
+    } else {
+        let node = this.tail;
+        while(size - index) {
+            node = node.prev;
+            index++;
+        }
+        return node;
+    }
+}
+
+DoublyLinkedList.prototype.deleteAtIndex = function(index) {
+    const { size } = this;
+    if (index < 0 || index >= size) {
+        return null;
+    }
+
+    let nodeToDelete = this.head;
+    if (index < size - index) {
+        while (index >= 0) {
+            nodeToDelete = nodeToDelete.next;
+            index--;
+        }
+    } else {
+        nodeToDelete = this.tail;
+        while(size - index) {
+            nodeToDelete = nodeToDelete.prev;
+            index++;
+        }
+    }
+    console.log('NODE TO DELETE>>', nodeToDelete);
+    const prevNode = nodeToDelete.prev;
+    const nextNode = nodeToDelete.next;
+    prevNode.next = nextNode;
+    nextNode.prev = prevNode;
+    nodeToDelete.prev = null;
+    nodeToDelete.next = null;
+    this.size--;
+}
+
+module.exports = DoublyLinkedList
+
+
+// ind 0, size 3, size - index = 3 
+// ind 3, size 3, size - index = 0
+// ind 1, size 3, size - index = 2
+// ind 2, size 3, size - index = 1
+// head ==== 3 ==== 4 === 5 === tail

doubly-linked-list/doubly-list-node.js

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+function DoublyListNode(value) {
+    this.value = value;
+    this.next = null;
+    this.prev = null;
+}
+
+module.exports = DoublyListNode;

doubly-linked-list/test-dll.js

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+const DoublyLinkedList = require("./doubly-linked-list");
+
+const dll = new DoublyLinkedList();
+
+dll.addAtHead(4);
+dll.addAtHead(5);
+dll.addAtHead(6); // 6  --> 5 ---> 4
+// console.log(dll.head.next);
+dll.addAtIndex(1, 12); // 6 === 12 === 5 === 4
+// console.log(dll.head.next);
+dll.deleteAtIndex(2);
+// console.log(dll.head.next);
+console.log(dll.getAtIndex(1).value);

linked-list/linked-list.js

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+// list node ---> elements/items
+
+const { ListNode } = require("./list-node");
+
+// { value: 4, next: null }
+
+// initialize --> head, size
+
+// Insert/Add at particular index, begin, end
+// Delete at a particular index, begin, end
+// Get the value of node at a particular index
+
+
+function LinkedList() {
+    this.head = new ListNode(0);
+    this.size = 0;
+}
+
+LinkedList.prototype.addAtIndex = function(index, value) {
+    if (index < 0 || index > this.size) {
+        return null;
+    }
+
+    let pre = this.head;
+    let i = 0;
+    while (i < index) {
+        pre = pre.next;
+        i++;
+    }
+
+    const currRef = pre.next;
+    const newNode = new ListNode(value);
+    pre.next = newNode;
+    newNode.next = currRef;
+    this.size += 1;
+}
+
+LinkedList.prototype.addAtStart = function(value) {
+    return this.addAtIndex(0, value);
+}
+
+LinkedList.prototype.deleteAtIndex = function(index) {
+    if (index < 0 || index >= this.size) {
+        return null;
+    }
+
+    let pre = this.head;
+    let i = 0;
+    while (i < index) {
+        pre = pre.next;
+        i++;
+    }
+
+    pre.next = pre.next.next;
+    this.size -= 1;
+}
+
+LinkedList.prototype.getNodeAtIndex = function(index) {
+    if (index < 0 || index > this.size) {
+        return null;
+    }
+
+    let pre = this.head;
+    let i = 0;
+    while (i <= index) {
+        pre = pre.next;
+        i++;
+    }
+
+    return pre.value;
+}
+
+exports.LinkedList = LinkedList
+/// sentinal ---> 1 ---> 2 -----> 3
+/// sentinal ---> 1 --> 5 --> 2 -----> 3

linked-list/list-node.js

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+function ListNode(value) {
+    this.value = value;
+    this.next = null;
+}
+
+exports.ListNode = ListNode

linked-list/test-ll.js

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+const { LinkedList } = require("./linked-list");
+
+const ll = new LinkedList();
+
+ll.addAtIndex(0, 15)
+ll.addAtIndex(0, 10)
+ll.addAtIndex(0, 5) // sentinal ---> 5 ---> 10 ---> 15
+console.log(JSON.stringify(ll.head));
+console.log(ll.getNodeAtIndex(2));
+ll.deleteAtIndex(2);
+console.log(JSON.stringify(ll.head));

map.js

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+const map = new Map();
+
+map.set("name", "John Doe");
+
+map.set(1, true);
+
+const obj = {
+    firstname: "Dummy Name"
+}
+
+map.set(obj, 3);
+
+// console.log(map);
+
+// console.log(map.get(obj));
+
+map.delete(2);
+console.log(map);

object.js

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+const person = {
+    firstname: "John",
+    lastname: "Doe",
+    age: 21,
+    greet: function() { return "Hello from " + this.firstname + " " + this.lastname }
+}
+console.log(person)
+
+console.log(person.greet())

set.js

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+const set = new Set();
+
+set.add(1);
+set.add("John");
+
+const obj = {
+    firstname: "dummy"
+}
+set.add(obj);
+
+set.add(1);
+console.log(set);
+console.log(set.delete(1))
+console.log(set);
+