LeetCode 2075 | Decode the Slanted Ciphertext | Java | Medium | Matrix Simulation | CodeByTushu
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In today’s video, we solve LeetCode 2075 — Decode the Slanted Ciphertext using String and Matrix Simulation in Java.
In this problem, an original text string is encoded using a slanted transposition cipher into a matrix with a fixed number of rows. The characters of the original text are written along downward-slanted diagonals from top-left to bottom-right, padding any empty cells with spaces so that the rightmost column remains non-empty. The encoded string is then generated by reading this matrix row by row. Given the encoded string and the number of rows, our goal is to reconstruct the original text and remove all trailing padding spaces.
To solve this efficiently, we first compute the column count by dividing the total length of the encoded string by the number of rows. Each cell at row r and column c maps directly to the 1D index r * cols + c. We reconstruct the original text by iterating through every starting column along the top row and walking down the diagonal as long as the column index stays within the matrix boundaries. Finally, we strip only the trailing spaces added by matrix padding while preserving necessary spaces between words. This results in an optimal linear time complexity of O(N) and O(N) auxiliary space.
🔥 Problem Highlights
✅ Direct 1D to 2D coordinate calculation: cols = N / rows
✅ Index mapping formula r * cols + (c + r) without extra matrix allocation
✅ Systematic diagonal path traversal from top-left to bottom-right
✅ Edge case handling for empty strings and single-row inputs
✅ Precise trailing space trimming to preserve internal word spacing
✅ Optimal O(N) time and O(N) auxiliary space complexity
⏱️ TIMESTAMPS
00:00 Intro & Daily Challenge Kickoff (Streak 98 Days)
01:25 Problem Understanding & Slanted Matrix Geometry
03:29 Key Insights: Direct 1D Indexing & Trailing Space Invariant
05:21 Optimal Linear Simulation Algorithm
06:54 Clean Java Solution Walkthrough Line by Line
08:07 Test Cases Dry Run & Benchmark Verification (15 ms, Beats 99.2%)
09:57 Time Complexity Analysis (O(N) Time)
10:57 Space Complexity Analysis (O(N) Auxiliary Space)
11:45 Day 4 Wrap-up & Channel Resources
📂 Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/solution.js
🔗 LeetCode Source Code
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💬 Question of the Day
Why do we only remove trailing spaces instead of all spaces in the decoded string?
1️⃣ Internal spaces are part of the original message while trailing spaces are matrix padding
2️⃣ All spaces in ciphertext are guaranteed to be encryption artifacts
3️⃣ Trailing spaces decrease string length and save memory
4️⃣ LeetCode requires all strings to be alphanumeric only
#LeetCode2075 #LeetCode #DecodeTheSlantedCiphertext #Java #JavaDSA #String #Matrix #Simulation #DSA #CodingInterview #ProblemSolving #LeetCodeMedium #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description
In today’s video, we solve LeetCode 2075 — Decode the Slanted Ciphertext using String and Matrix Simulation in Java.
In this problem, an original text string is encoded using a slanted transposition cipher into a matrix with a fixed number of rows. The characters of the original text are written along downward-slanted diagonals from top-left to bottom-right, padding any empty cells with spaces so that the rightmost column remains non-empty. The encoded string is then generated by reading this matrix row by row. Given the encoded string and the number of rows, our goal is to reconstruct the original text and remove all trailing padding spaces.
To solve this efficiently, we first compute the column count by dividing the total length of the encoded string by the number of rows. Each cell at row r and column c maps directly to the 1D index r * cols + c. We reconstruct the original text by iterating through every starting column along the top row and walking down the diagonal as long as the column index stays within the matrix boundaries. Finally, we strip only the trailing spaces added by matrix padding while preserving necessary spaces between words. This results in an optimal linear time complexity of O(N) and O(N) auxiliary space.
🔥 Problem Highlights
✅ Direct 1D to 2D coordinate calculation: cols = N / rows
✅ Index mapping formula r * cols + (c + r) without extra matrix allocation
✅ Systematic diagonal path traversal from top-left to bottom-right
✅ Edge case handling for empty strings and single-row inputs
✅ Precise trailing space trimming to preserve internal word spacing
✅ Optimal O(N) time and O(N) auxiliary space complexity
⏱️ TIMESTAMPS
00:00 Intro & Daily Challenge Kickoff (Streak 98 Days)
01:25 Problem Understanding & Slanted Matrix Geometry
03:29 Key Insights: Direct 1D Indexing & Trailing Space Invariant
05:21 Optimal Linear Simulation Algorithm
06:54 Clean Java Solution Walkthrough Line by Line
08:07 Test Cases Dry Run & Benchmark Verification (15 ms, Beats 99.2%)
09:57 Time Complexity Analysis (O(N) Time)
10:57 Space Complexity Analysis (O(N) Auxiliary Space)
11:45 Day 4 Wrap-up & Channel Resources
📂 Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/April/04-April/2075-Decode-the-Slanted-Ciphertext/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 Medium Problems
Java DSA Preparation
String Manipulation Patterns
Matrix Index Mapping
Simulation Problems
Time Complexity Optimization
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 do we only remove trailing spaces instead of all spaces in the decoded string?
1️⃣ Internal spaces are part of the original message while trailing spaces are matrix padding
2️⃣ All spaces in ciphertext are guaranteed to be encryption artifacts
3️⃣ Trailing spaces decrease string length and save memory
4️⃣ LeetCode requires all strings to be alphanumeric only
#LeetCode2075 #LeetCode #DecodeTheSlantedCiphertext #Java #JavaDSA #String #Matrix #Simulation #DSA #CodingInterview #ProblemSolving #LeetCodeMedium #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description
