add queue and stack

Author: dingjy94

README.md

@@ -1,5 +1,12 @@
 # Algorithm and Data Structure
 My personal note learn JavaScript
 
+## Curriculum
+This curriculum based on the one of (ACM-ICPC-Preparation)[https://github.com/NAU-ACM/ACM-ICPC-Preparation], but didn't follow the order.
+
+|     | Data Structure | Algorithm | Tutorial | Questions |
+| --- | -------------- | --------- | -------- | --------- |
+| 1   | <ul><li>[Queue](/dataStructure/queue/queue.js)</li><li>[Stack](/dataStructure/stack/stack.js)</li></ul> | <ul><li>DFS</li><li>BFS</li></ul> | [Data Structures: Stacks and Queues (Youtube)](https://www.youtube.com/watch?v=wjI1WNcIntg) | <ul><li>[ Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)</li><li>[Largest Rectangle in Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram/)[\(my solution\)](/questions/largestRectangleArea.js)</li></ul>|
+
 ## algorithm
 1. [useful tricky (tricky methods depends on JavaScript features)](/algorithm/useful_trick.md)

dataStructure/queue/queue.js

@@ -0,0 +1,48 @@
+class Node {
+  constructor (val, next = null) {
+    this.val = val;
+    this.next = next;
+  }
+}
+
+export default class Queue {
+  constructor () {
+    this.head = null;
+    this.tail = null;
+  }
+
+  isEmpty() {
+    return !this.tail;
+  }
+
+  peek() {
+    return this.head.val;
+  }
+
+  add(val) {
+    const newNode = new Node(val);
+    if (this.tail) {
+      this.tail.next = newNode;
+    }
+    this.tail = newNode;
+
+    if (!this.head) {
+      this.head = newNode;
+    }
+  }
+
+  remove() {
+    if (this.isEmpty()) {
+      throw new Error('The queue is empty!');
+    }
+
+    const headVal = this.head.val;
+    this.head = this.head.next;
+
+    if (!this.head) {
+      this.tail = null;
+    }
+
+    return headVal;
+  }
+}

dataStructure/queue/queue.test.js

@@ -0,0 +1,29 @@
+import Queue from "./queue";
+
+describe('Queue', () => {
+  const queue = new Queue();
+
+  it('should init a empty queue', () => {
+    expect(queue.isEmpty()).toBeTruthy();
+  });
+
+  it('should add 1 in queue', () => {
+    queue.add(1);
+    expect(queue.isEmpty()).toBeFalsy();
+    expect(queue.peek()).toBe(1);
+  });
+
+  it('should push 2 in queue, peek should return 1', () => {
+    queue.add(2);
+    expect(queue.peek()).toBe(1);
+  });
+
+  it('should remove 1', () => {
+    expect(queue.remove()).toBe(1);
+  });
+
+  it('should remove 2, and queue is empty', () => {
+    expect(queue.remove()).toBe(2);
+    expect(queue.isEmpty()).toBeTruthy();
+  })
+});

dataStructure/stack/stack.js

@@ -0,0 +1,39 @@
+class Node {
+  constructor (val, next = null) {
+    this.val = val;
+    this.next = next;
+  }
+}
+
+export default class Stack {
+  constructor () {
+    this.top = null;
+  }
+
+  isEmpty() {
+    return !this.top;
+  }
+
+  peek() {
+    return this.top.val;
+  }
+
+  push(val) {
+    const newNode = new Node(val);
+
+    if (this.top) {
+      newNode.next = this.top;
+    }
+    this.top = newNode;
+  }
+
+  pop() {
+    if (this.isEmpty()) {
+      throw new Error('The stack is empty');
+    }
+
+    const curVal = this.top.val;
+    this.top = this.top.next;
+    return curVal;
+  }
+}

dataStructure/stack/stack.test.js

@@ -0,0 +1,30 @@
+import Stack from "./stack";
+
+describe('Stack', () => {
+  const stack = new Stack();
+
+  it('should init a empty Stack', () => {
+    expect(stack.isEmpty()).toBeTruthy();
+  });
+
+  it('should push 1 in stack', () => {
+    stack.push(1);
+    expect(stack.isEmpty()).toBeFalsy();
+    expect(stack.peek()).toBe(1);
+  });
+
+  it('should push 2 in stack, peek should return 2', () => {
+    stack.push(2);
+    expect(stack.peek()).toBe(2);
+  });
+
+  it('should pop 2', () => {
+    expect(stack.pop()).toBe(2);
+  });
+
+  it('should pop 1, and stack is empty', () => {
+    expect(stack.pop()).toBe(1);
+    expect(stack.isEmpty()).toBeTruthy();
+  })
+});
+

questions/largestRectangleArea.js

@@ -0,0 +1,39 @@
+/**
+ * Given n non-negative integers representing the histogram's bar height where the width of each bar is 1,
+ * find the area of largest rectangle in the histogram.
+ * https://leetcode.com/problems/largest-rectangle-in-histogram/
+ *
+ * @param {number[]} heights
+ * @return {number}
+ */
+
+/**
+ * 1. We need to caculate areas when each bar is the smallest bar;
+ * 2. This means to find the last left bar smaller than current bar, and first right bar smaller than current bar.
+ * 3. right is simple. In order to find the left, maintain a stack, in which the smaller bar in bottom.
+ * 4. loop through bars (from left to right), if cur bar larger than the one in top of the stack, just push in.
+ * 5. If cur bar smaller than top, cur bar is the right bar of the top bar. The bar under top is the left one.
+ */
+var largestRectangleArea = function(heights) {
+  const stack = [];
+  let i = 0;
+  let maxArea = 0;
+
+  while (i < heights.length) {
+    if (!stack.length || heights[i] >= heights[stack[stack.length - 1]]) {
+      stack.push(i++);
+    } else {
+      const top = stack.pop();
+      const curArea = heights[top] * (stack.length ? i - stack[stack.length - 1] - 1 : i);
+      maxArea = Math.max(maxArea, curArea);
+    }
+  }
+
+  while (stack.length) {
+    const top = stack.pop();
+    const curArea = heights[top] * (stack.length ? i - stack[stack.length - 1] - 1 : i);
+    maxArea = Math.max(maxArea, curArea);
+  }
+
+  return maxArea;
+};