LeetCode 67 | Add Binary | Java | Easy | Two Pointers & Carry Bit Simulation | CodeByTushu
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In today’s video, we solve LeetCode 67 — Add Binary using Math, String, and Bit Manipulation in Java.
We are given two binary strings a and b representing non-negative integers in base 2. We need to compute and return their binary sum as a string without converting them to standard 32-bit or 64-bit integers, as the string lengths can extend up to 10,000 characters and cause integer overflows. By applying column-by-column base-2 arithmetic starting from the least significant bits at the end of both strings, we can simulate full-adder logic directly on character sequences.
Using two pointers traversing right-to-left along with a carry accumulator, each step computes the total sum of the current digits plus carry. The resulting digit is determined by sum % 2, while the new carry forwarded to the next position is given by sum / 2. The loop runs cleanly until both strings and the trailing carry bit are fully exhausted. Reversing the collected digits yields the final binary answer in optimal O(max(N, M)) time complexity and O(max(N, M)) auxiliary space.
🔥 Problem Highlights
✅ Grade-school binary addition logic without integer overflow
✅ Two-pointer right-to-left bit scanning
✅ Full-adder simulation (sum % 2 for bit value, sum / 2 for carry)
✅ Single while-loop handling strings of different lengths and trailing carry
✅ Linear O(max(N, M)) time complexity capable of handling N, M up to 10^4
✅ Memory-efficient StringBuilder reversal
⏱️ TIMESTAMPS
00:00 Intro
01:11 Problem Understanding & Constraints
02:21 Elementary Binary Addition & Carry Insight
03:40 Two-Pointer Column-Wise Strategy
05:03 Java Code Walkthrough Line by Line
06:19 Test Cases Walkthrough & Simulation
07:46 Time Complexity Analysis (O(max(N, M)))
08:35 Space Complexity Analysis (O(max(N, M)))
09:13 Outro & Wrap-up
📂 Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/February/15-February/67-Add-Binary
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/solution.js
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💬 Question of the Day
When adding two binary digits with a carry bit, what is the maximum possible value of `sum` in base 2 addition?
1️⃣ 1
2️⃣ 2
3️⃣ 3 (when both bits are '1' and carry is 1)
4️⃣ 4
#LeetCode67 #LeetCode #AddBinary #Java #JavaDSA #Math #BitManipulation #String #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description
In today’s video, we solve LeetCode 67 — Add Binary using Math, String, and Bit Manipulation in Java.
We are given two binary strings a and b representing non-negative integers in base 2. We need to compute and return their binary sum as a string without converting them to standard 32-bit or 64-bit integers, as the string lengths can extend up to 10,000 characters and cause integer overflows. By applying column-by-column base-2 arithmetic starting from the least significant bits at the end of both strings, we can simulate full-adder logic directly on character sequences.
Using two pointers traversing right-to-left along with a carry accumulator, each step computes the total sum of the current digits plus carry. The resulting digit is determined by sum % 2, while the new carry forwarded to the next position is given by sum / 2. The loop runs cleanly until both strings and the trailing carry bit are fully exhausted. Reversing the collected digits yields the final binary answer in optimal O(max(N, M)) time complexity and O(max(N, M)) auxiliary space.
🔥 Problem Highlights
✅ Grade-school binary addition logic without integer overflow
✅ Two-pointer right-to-left bit scanning
✅ Full-adder simulation (sum % 2 for bit value, sum / 2 for carry)
✅ Single while-loop handling strings of different lengths and trailing carry
✅ Linear O(max(N, M)) time complexity capable of handling N, M up to 10^4
✅ Memory-efficient StringBuilder reversal
⏱️ TIMESTAMPS
00:00 Intro
01:11 Problem Understanding & Constraints
02:21 Elementary Binary Addition & Carry Insight
03:40 Two-Pointer Column-Wise Strategy
05:03 Java Code Walkthrough Line by Line
06:19 Test Cases Walkthrough & Simulation
07:46 Time Complexity Analysis (O(max(N, M)))
08:35 Space Complexity Analysis (O(max(N, M)))
09:13 Outro & Wrap-up
📂 Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/February/15-February/67-Add-Binary
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/February/15-February/67-Add-Binary/solution.js
🔗 LeetCode Source Code
📌 Admin type the link
🌐 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 & Math
Binary Arithmetic
String Pointer Techniques
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
When adding two binary digits with a carry bit, what is the maximum possible value of `sum` in base 2 addition?
1️⃣ 1
2️⃣ 2
3️⃣ 3 (when both bits are '1' and carry is 1)
4️⃣ 4
#LeetCode67 #LeetCode #AddBinary #Java #JavaDSA #Math #BitManipulation #String #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description