advanced

JavaScript Queues - Advanced Level

This section covers advanced difficulty queue problems from LeetCode, implemented using modern ES6+ JavaScript features.

Problems

1. Number of Visible People in a Queue
2. Shortest Subarray with Sum at Least K
3. Find the Most Competitive Subsequence

Approaches

Each problem is solved using multiple approaches showcasing different JavaScript features and patterns:

Problem 1: Number of Visible People in a Queue

• Approach 1: Stack-based Solution (Optimal)
• Approach 2: Brute Force Solution
• Approach 3: Monotonic Stack Solution with Detailed Tracking
• Approach 4: Functional Programming Solution
• Approach 5: Recursive Solution with Memoization
• Approach 6: Generator-based Solution with Step-by-Step Visualization

Problem 2: Shortest Subarray with Sum at Least K

• Approach 1: Deque-based Solution (Optimal)
• Approach 2: Brute Force Solution
• Approach 3: Sliding Window with Prefix Sums
• Approach 4: Functional Programming Solution
• Approach 5: Priority Queue Solution
• Approach 6: Generator-based Solution with Step-by-Step Visualization

Problem 3: Find the Most Competitive Subsequence

• Approach 1: Stack-based Solution (Optimal)
• Approach 2: Brute Force Solution
• Approach 3: Monotonic Stack Solution with Detailed Tracking
• Approach 4: Functional Programming Solution
• Approach 5: Recursive Solution with Memoization
• Approach 6: Generator-based Solution with Step-by-Step Visualization

Key JavaScript Features Used

• ES6+ syntax (arrow functions, destructuring, spread operator)
• Modern data structures (Map, Set)
• Functional programming patterns
• Factory functions
• Custom iterators with Symbol.iterator
• Generator functions for step-by-step visualization
• Performance testing utilities
• Comprehensive documentation with time/space complexity analysis

Usage

Each implementation file can be run independently to see the implementation in action:

node answer1.js
node answer2.js
node answer3.js

Performance Comparison

All implementations include performance testing utilities to compare different approaches:

// Performance comparison utility
const performanceTest = (func, name, nums, k) => {
  const start = performance.now();
  func([...nums], k);
  const end = performance.now();
  console.log(`${name}: ${end - start}ms for array of size ${nums.length} with k=${k}`);
};

Source

Problems from LeetCode Very Hard:

• https://leetcode.com/problems/number-of-visible-people-in-a-queue/
• https://leetcode.com/problems/shortest-subarray-with-sum-at-least-k/
• https://leetcode.com/problems/find-the-most-competitive-subsequence/