LeetCode 190 | Reverse Bits | Java | Easy | Bit Manipulation & Mask Swapping | CodeByTushu
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In today’s video, we solve LeetCode 190 — Reverse Bits using Bit Manipulation and Divide and Conquer in Java.
We are given a 32-bit integer named n and need to reverse the order of its binary representation, from the most significant bit to the least significant bit. To reverse the bits, we iterate through all 32 bit positions, extracting the current least significant bit using the bitwise AND operation between n and 1. We then add that bit to our result using left shift operations.
During each iteration, we shift the result one position to the left and add the extracted bit. Meanwhile, the input number is shifted logically to the right using Java's unsigned right shift operator. This prevents the sign bit from being extended during the operation.
We also discuss advanced optimizations for interview follow-up questions when the function is called repeatedly. These include divide-and-conquer bit swapping with masks and precomputed 8-bit lookup tables, which can reverse bits efficiently using constant-time operations and constant auxiliary space.
🔥 Problem Highlights
✅ Extracted bits from right to left using the bitwise AND operation
✅ Built the reversed result using left shifts and bitwise OR operations
✅ Used unsigned logical right shift to prevent sign extension
✅ Applied a strict 32-iteration loop for exact 32-bit reversal
✅ Explored divide-and-conquer bit swapping with masks
✅ Achieved O(1) time complexity and O(1) auxiliary space
⏱️ TIMESTAMPS
00:00 Intro and Problem Overview
01:17 Problem Understanding and Constraints
02:50 Bit Extraction and Unsigned Logical Shift
04:15 32-Bit Traversal and Byte Lookup Optimization
05:34 Java Solution Walkthrough Line by Line
06:44 Test Cases Walkthrough and Simulation
08:05 Time Complexity Analysis O(1)
08:52 Space Complexity Analysis O(1)
09:23 Outro and Wrap-up
📂 Problem Folder and Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/February/16-February/190-Reverse-Bits
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/solution.js
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🔥 Perfect For
LeetCode Easy Problems
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Divide and Conquer Mask Swaps
Binary Bit-Level Operations
Coding Interview Preparation
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💬 Question of the Day
Why must we use Java's unsigned logical right shift operator instead of the arithmetic right shift operator when reversing bits?
1️⃣ Because Java does not allow arithmetic right shift inside a for loop
2️⃣ Because unsigned right shift fills empty high-order bit positions with zeros, while arithmetic right shift preserves the sign bit and may fill empty positions with ones for negative numbers
3️⃣ Because unsigned right shift always executes twice as fast on modern CPUs
4️⃣ Because arithmetic right shift can only be used with 64-bit long variables
#LeetCode190 #LeetCode #ReverseBits #Java #JavaDSA #BitManipulation #DivideAndConquer #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description
In today’s video, we solve LeetCode 190 — Reverse Bits using Bit Manipulation and Divide and Conquer in Java.
We are given a 32-bit integer named n and need to reverse the order of its binary representation, from the most significant bit to the least significant bit. To reverse the bits, we iterate through all 32 bit positions, extracting the current least significant bit using the bitwise AND operation between n and 1. We then add that bit to our result using left shift operations.
During each iteration, we shift the result one position to the left and add the extracted bit. Meanwhile, the input number is shifted logically to the right using Java's unsigned right shift operator. This prevents the sign bit from being extended during the operation.
We also discuss advanced optimizations for interview follow-up questions when the function is called repeatedly. These include divide-and-conquer bit swapping with masks and precomputed 8-bit lookup tables, which can reverse bits efficiently using constant-time operations and constant auxiliary space.
🔥 Problem Highlights
✅ Extracted bits from right to left using the bitwise AND operation
✅ Built the reversed result using left shifts and bitwise OR operations
✅ Used unsigned logical right shift to prevent sign extension
✅ Applied a strict 32-iteration loop for exact 32-bit reversal
✅ Explored divide-and-conquer bit swapping with masks
✅ Achieved O(1) time complexity and O(1) auxiliary space
⏱️ TIMESTAMPS
00:00 Intro and Problem Overview
01:17 Problem Understanding and Constraints
02:50 Bit Extraction and Unsigned Logical Shift
04:15 32-Bit Traversal and Byte Lookup Optimization
05:34 Java Solution Walkthrough Line by Line
06:44 Test Cases Walkthrough and Simulation
08:05 Time Complexity Analysis O(1)
08:52 Space Complexity Analysis O(1)
09:23 Outro and Wrap-up
📂 Problem Folder and Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/February/16-February/190-Reverse-Bits
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/16-February/190-Reverse-Bits/solution.js
🔗 LeetCode Source Code
📌 Add the link here
🌐 All LeetCode Solutions
📌 https://codebytushu.com/Leetcode/
📱 Join CodeByTushu on WhatsApp
Get coding updates, LeetCode solutions, daily questions and more.
https://whatsapp.com/channel/0029Vb8k5mCDeON2Xwlkxe40
❤️ Donate
📌 https://codebytushu.com/Leetcode/donate.php
🔥 Perfect For
LeetCode Easy Problems
Java DSA Preparation
Bit Manipulation Mastery
Divide and Conquer Mask Swaps
Binary Bit-Level Operations
Coding Interview Preparation
Problem Solving
🌐 Follow CodeByTushu
▶️ YouTube: https://www.youtube.com/@codebytushu
📸 Instagram: https://instagram.com/codebytushu/
💼 LinkedIn: https://www.linkedin.com/company/codebytushu/
🌍 Website: https://codebytushu.com
🐙 GitHub: https://github.com/CodeByTushu
❤️ Don’t Forget To
👍 Like | 💬 Comment | 🔔 Subscribe
💬 Question of the Day
Why must we use Java's unsigned logical right shift operator instead of the arithmetic right shift operator when reversing bits?
1️⃣ Because Java does not allow arithmetic right shift inside a for loop
2️⃣ Because unsigned right shift fills empty high-order bit positions with zeros, while arithmetic right shift preserves the sign bit and may fill empty positions with ones for negative numbers
3️⃣ Because unsigned right shift always executes twice as fast on modern CPUs
4️⃣ Because arithmetic right shift can only be used with 64-bit long variables
#LeetCode190 #LeetCode #ReverseBits #Java #JavaDSA #BitManipulation #DivideAndConquer #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description