LeetCode 1980 | Unique Binary String Problem Explained Step-by-Step

Описание: 🚀 LeetCode 1980 – Find Unique Binary String | Cantor’s Diagonal Trick Explained

In this video, we solve LeetCode Problem 1980: Find Unique Binary String, a very interesting string + mathematical observation problem that appears in coding interviews.

You are given an array nums containing n unique binary strings, each of length n.
Your task is to return a binary string of length n that does NOT appear in the array.

For example:

Input:
nums = ["01","10"]

Output:
"11" (or "00")

The key observation is that we can construct a guaranteed unique binary string using Cantor’s Diagonalization Trick.

Instead of checking every possible binary string (which would be exponential), we build a new string by flipping the diagonal bits of the input strings.

This ensures the new string differs from every string in the array at least in one position, guaranteeing uniqueness.

⏱ Time Complexity: O(n)
📦 Space Complexity: O(n)

This problem helps you understand an elegant concept used in mathematics, set theory, and algorithm design.

💻 Code & Notes Repository

🔗 All LeetCode Solutions Repository
https://github.com/Gopalkushwaha1/Lee...

🔗 AlgoDiary Interview Notes + Structured Code
https://github.com/Gopalkushwaha1/Alg...

🔗 Direct Problem Folder (1980)
https://github.com/Gopalkushwaha1/Alg...

🔗 Direct Java Solution File
https://github.com/Gopalkushwaha1/Alg...

🔗 Direct Python Solution File
https://github.com/Gopalkushwaha1/Alg...

🔥 What you will learn in this video

• Understanding the problem intuition
• Why Brute Force (2ⁿ possibilities) is inefficient
• The powerful Cantor’s Diagonalization Trick
• How to build a guaranteed unique binary string
• Step-by-step optimal solution explanation
• Time and Space Complexity analysis
• Clean and simple Java implementation

🎯 Who should watch this video?

• Students preparing for coding interviews
• Beginners learning Data Structures and Algorithms
• Developers practicing LeetCode medium problems
• Anyone who wants to learn smart mathematical tricks in algorithms

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#LeetCode #DSA #BinaryString #CodingInterview #Algorithms #Java

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