From 62f1cfe0cd6afbd950045c58ed5e88e243df3173 Mon Sep 17 00:00:00 2001
From: atulll <39869656+underager@users.noreply.github.com>
Date: Fri, 3 Dec 2021 00:09:23 +0530
Subject: [PATCH] chore(JavaScript): add stack and queue implementation (#639)

---
 algorithms/JavaScript/README.md               |  7 ++
 algorithms/JavaScript/src/index.js            |  7 ++
 algorithms/JavaScript/src/queues/queue.js     | 54 +++++++++++++
 algorithms/JavaScript/src/stacks/stack.js     | 29 +++++++
 algorithms/JavaScript/src/stacks/two-stack.js | 78 +++++++++++++++++++
 5 files changed, 175 insertions(+)
 create mode 100644 algorithms/JavaScript/src/queues/queue.js
 create mode 100644 algorithms/JavaScript/src/stacks/stack.js
 create mode 100644 algorithms/JavaScript/src/stacks/two-stack.js

diff --git a/algorithms/JavaScript/README.md b/algorithms/JavaScript/README.md
index e51c9313..3034ad0d 100644
--- a/algorithms/JavaScript/README.md
+++ b/algorithms/JavaScript/README.md
@@ -22,3 +22,10 @@
 ## Strings
 - [Palindrome](src/strings/palindrome.js)
 - [Sequence](src/strings/sequence.js)
+
+## Stacks
+- [Stacks](src/stacks/stack.js)
+- [Two Stack](src/stacks/two-stack.js)
+
+## Queues
+- [Queue](src/queues/queue.js)
diff --git a/algorithms/JavaScript/src/index.js b/algorithms/JavaScript/src/index.js
index 214b8f7f..f85a9fe7 100644
--- a/algorithms/JavaScript/src/index.js
+++ b/algorithms/JavaScript/src/index.js
@@ -19,3 +19,10 @@ require('./sorting/selection-sort');
 // Strings
 require('./strings/palindrome');
 require('./strings/sequence');
+
+// Stack
+require('./stacks/stack');
+require('./stacks/two-stack')
+
+// Queue
+require('./queues/queue');
diff --git a/algorithms/JavaScript/src/queues/queue.js b/algorithms/JavaScript/src/queues/queue.js
new file mode 100644
index 00000000..6e48139b
--- /dev/null
+++ b/algorithms/JavaScript/src/queues/queue.js
@@ -0,0 +1,54 @@
+class Node {
+  constructor(value) {
+    this.value = value;
+    this.next = null;
+  }
+}
+
+class Queue {
+  constructor() {
+    this.first = null;
+    this.last = null;
+    this.size = 0;
+  }
+
+  enqueue(value) {
+    const newNode = new Node(value);
+    if (!this.first) {
+      this.first = newNode;
+      this.last = newNode;
+    } else {
+      this.last.next = newNode;
+      this.last = newNode;
+    }
+    this.size++;
+  }
+
+  dequeue() {
+    if (!this.first) return null;
+    const temp = this.first;
+    this.first = this.first.next;
+    this.size--;
+    return temp.value;
+  }
+
+  printQueue() {
+    let current = this.first;
+    while (current) {
+      console.log(current.value);
+      current = current.next;
+    }
+  }
+}
+
+const queue = new Queue();
+queue.enqueue(1);
+queue.enqueue(2);
+queue.enqueue(3);
+queue.enqueue(4);
+
+queue.printQueue();
+
+queue.dequeue();
+
+queue.printQueue();
diff --git a/algorithms/JavaScript/src/stacks/stack.js b/algorithms/JavaScript/src/stacks/stack.js
new file mode 100644
index 00000000..8799e49f
--- /dev/null
+++ b/algorithms/JavaScript/src/stacks/stack.js
@@ -0,0 +1,29 @@
+class Stack {
+  constructor() {
+    this.items = [];
+  }
+
+  push(element) {
+    this.items.push(element);
+  }
+
+  pop() {
+    return this.items.pop();
+  }
+
+  printStack() {
+    console.log(this.items);
+  }
+}
+
+const stack = new Stack();
+stack.push(1);
+stack.push(2);
+stack.push(3);
+stack.push(4);
+
+stack.printStack();
+
+console.log(stack.pop());
+
+stack.printStack();
diff --git a/algorithms/JavaScript/src/stacks/two-stack.js b/algorithms/JavaScript/src/stacks/two-stack.js
new file mode 100644
index 00000000..84a65b0c
--- /dev/null
+++ b/algorithms/JavaScript/src/stacks/two-stack.js
@@ -0,0 +1,78 @@
+// Implement Stack using two queues
+class Stack {
+  constructor() {
+    this.queue1 = new Queue();
+    this.queue2 = new Queue();
+  }
+
+  push(value) {
+    this.queue1.enqueue(value);
+  }
+
+  pop() {
+    if (!this.queue1.first) return null;
+    while (this.queue1.size > 1) {
+      this.queue2.enqueue(this.queue1.dequeue());
+    }
+    const temp = this.queue1.dequeue();
+    this.queue1 = this.queue2;
+    this.queue2 = new Queue();
+    return temp;
+  }
+
+  printStack() {
+    if (this.queue1.size === 0) return null;
+    let current = this.queue1.first;
+    while (current) {
+      console.log(current.value);
+      current = current.next;
+    }
+  }
+}
+
+class Node {
+  constructor(value) {
+    this.value = value;
+    this.next = null;
+  }
+}
+
+class Queue {
+  constructor() {
+    this.first = null;
+    this.last = null;
+    this.size = 0;
+  }
+
+  enqueue(value) {
+    const newNode = new Node(value);
+    if (!this.first) {
+      this.first = newNode;
+      this.last = newNode;
+    } else {
+      this.last.next = newNode;
+      this.last = newNode;
+    }
+    this.size++;
+  }
+
+  dequeue() {
+    if (!this.first) return null;
+    const temp = this.first;
+    this.first = this.first.next;
+    this.size--;
+    return temp.value;
+  }
+}
+
+const stack = new Stack();
+stack.push(1);
+stack.push(2);
+stack.push(3);
+stack.push(4);
+
+stack.printStack();
+
+console.log(stack.pop());
+
+stack.printStack();