LeetCode Queue Problems - Complete Collection

A comprehensive collection of 20 LeetCode queue problems with detailed solutions, explanations, and test cases.

📚 Project Overview

This collection covers queue problems across four categories:

• Basic Queue Operations (5 problems)
• Deque Operations (5 problems)
• Priority Queue (5 problems)
• Advanced Patterns (5 problems)

Each problem includes:

• ✅ Complete problem description with constraints
• ✅ Optimized solution with inline comments
• ✅ Time and space complexity analysis
• ✅ Detailed explanation of the approach
• ✅ Comprehensive test cases (normal + edge cases)
• ✅ Key insights and related problems

📊 Problem Index

#	Title	Difficulty	Category	Time	Space
1	Implement Queue using Stacks	Easy	Basic Operations	O(1)	O(n)
2	Number of Recent Calls	Easy	Basic Operations	O(1)	O(n)
3	Moving Average from Data Stream	Easy	Basic Operations	O(1)	O(n)
4	Reveal Cards In Increasing Order	Medium	Basic Operations	O(n log n)	O(n)
5	Time Based Key-Value Store	Medium	Basic Operations	O(log n)	O(n)
6	Sliding Window Maximum	Hard	Deque Operations	O(n)	O(n)
7	Sliding Window Median	Hard	Deque Operations	O(n log n)	O(n)
8	Dota2 Senate	Medium	Deque Operations	O(n)	O(n)
9	Zigzag Iterator	Medium	Deque Operations	O(1)	O(1)
10	Implement Deque	Medium	Deque Operations	O(1)	O(n)
11	Kth Largest Element in Stream	Easy	Priority Queue	O(log k)	O(k)
12	Reorganize String	Medium	Priority Queue	O(n log n)	O(1)
13	Task Scheduler	Medium	Priority Queue	O(n)	O(1)
14	Rearrange String k Distance Apart	Medium	Priority Queue	O(n log n)	O(1)
15	Furthest Building You Can Reach	Hard	Priority Queue	O(n log n)	O(n)
16	Shortest Path in Binary Matrix	Medium	Advanced Patterns	O(n*m)	O(n*m)
17	Rotting Oranges	Medium	Advanced Patterns	O(n*m)	O(n*m)
18	Walls and Gates	Medium	Advanced Patterns	O(n*m)	O(n*m)
19	Number of Islands II	Hard	Advanced Patterns	O(n log n)	O(n)
20	Trapping Rain Water II	Hard	Advanced Patterns	O(nm log(nm))	O(n*m)

🚀 Quick Start

cd solutions/java
javac *.java
java ImplementQueueUsingStacks

🎯 Learning Path

1. Start with Basic Queue Operations to understand queue fundamentals
2. Move to Deque Operations to learn double-ended queue techniques
3. Explore Priority Queue for ordered processing
4. Master Advanced Patterns for complex applications

📝 Each Problem Includes

• Problem Description
• Constraints
• Examples
• Solution with comments
• Complexity Analysis
• Approach Explanation
• Key Insights
• Related Problems
• Test Cases

🔧 Technologies

• Java 8+ - Primary implementation language
• Queue, Deque, PriorityQueue - Core data structures

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Happy Learning! 🎓