LeetCode 2946 | Matrix Similarity After Cyclic Shifts | Java | Easy | Simulation | CodeByTushu
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In today’s video, we solve LeetCode 2946 — Matrix Similarity After Cyclic Shifts using Simulation, Modulo Arithmetic, and Matrix Manipulation in Java.
In this problem, we are given an m by n matrix and an integer k. In each of the k steps, even-indexed rows are cyclically shifted to the left, and odd-indexed rows are cyclically shifted to the right. We need to determine if the matrix after k cyclic shifts remains identical to its original configuration.
Instead of performing a full step-by-step matrix simulation, we leverage modular arithmetic to reduce k modulo n. Moreover, an array is invariant under a cyclic left shift of k steps if and only if it is invariant under a cyclic right shift of k steps. By simply checking whether mat[i][j] equals mat[i][(j + k) % n] across all cells, we achieve an optimal O(m * n) time and O(1) auxiliary space solution.
🔥 Problem Highlights
✅ Periodic property of cyclic permutations reducing k modulo n
✅ Mathematical symmetry between cyclic left shift and cyclic right shift invariance
✅ Avoiding redundant matrix copies through direct index projection
✅ Instant early exit when k % n equals 0 or upon first mismatch
✅ Clean, concise, and memory-optimal implementation
✅ Optimal O(m * n) time complexity and O(1) auxiliary space
⏱️ TIMESTAMPS
00:00 Intro & Daily Challenge Overview
01:24 Problem Understanding & Cyclic Shift Rules
03:39 Key Mathematical Observation: Left & Right Shift Equivalence
05:47 Algorithmic Strategy & Modulo Optimization
07:09 Clean Java Solution Walkthrough Line by Line
08:19 Dry Run & Step-by-Step Example Walkthrough
10:35 Time Complexity Analysis (O(M × N) - 0 ms, Beats 100%)
11:49 Space Complexity Analysis (O(1) Auxiliary Space)
12:39 Outro & Resources
📂 Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/solution.js
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💬 Question of the Day
Why is checking mat[i][j] == mat[i][(j + k) % n] sufficient for both left-shifted even rows and right-shifted odd rows?
1️⃣ Because any array invariant under a cyclic left shift of k steps is symmetrically invariant under a cyclic right shift of k steps
2️⃣ Because odd rows are ignored if k is an even number
3️⃣ Because the matrix is guaranteed to be a square matrix
4️⃣ Because shifting right by k is identical to shifting left by n - k only when k is zero
#LeetCode2946 #LeetCode #MatrixSimilarityAfterCyclicShifts #Java #JavaDSA #Matrix #Simulation #Array #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
👇 Comment the answer below! 🔥 Close description
In today’s video, we solve LeetCode 2946 — Matrix Similarity After Cyclic Shifts using Simulation, Modulo Arithmetic, and Matrix Manipulation in Java.
In this problem, we are given an m by n matrix and an integer k. In each of the k steps, even-indexed rows are cyclically shifted to the left, and odd-indexed rows are cyclically shifted to the right. We need to determine if the matrix after k cyclic shifts remains identical to its original configuration.
Instead of performing a full step-by-step matrix simulation, we leverage modular arithmetic to reduce k modulo n. Moreover, an array is invariant under a cyclic left shift of k steps if and only if it is invariant under a cyclic right shift of k steps. By simply checking whether mat[i][j] equals mat[i][(j + k) % n] across all cells, we achieve an optimal O(m * n) time and O(1) auxiliary space solution.
🔥 Problem Highlights
✅ Periodic property of cyclic permutations reducing k modulo n
✅ Mathematical symmetry between cyclic left shift and cyclic right shift invariance
✅ Avoiding redundant matrix copies through direct index projection
✅ Instant early exit when k % n equals 0 or upon first mismatch
✅ Clean, concise, and memory-optimal implementation
✅ Optimal O(m * n) time complexity and O(1) auxiliary space
⏱️ TIMESTAMPS
00:00 Intro & Daily Challenge Overview
01:24 Problem Understanding & Cyclic Shift Rules
03:39 Key Mathematical Observation: Left & Right Shift Equivalence
05:47 Algorithmic Strategy & Modulo Optimization
07:09 Clean Java Solution Walkthrough Line by Line
08:19 Dry Run & Step-by-Step Example Walkthrough
10:35 Time Complexity Analysis (O(M × N) - 0 ms, Beats 100%)
11:49 Space Complexity Analysis (O(1) Auxiliary Space)
12:39 Outro & Resources
📂 Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts
☕ Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/Solution.java
🐍 Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/solution.py
⚡ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/solution.cpp
🌐 JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/March/27-March/2946-Matrix-Similarity-After-Cyclic-Shifts/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
Matrix Manipulation Patterns
Modulo Arithmetic & Invariants
Array Indexing Techniques
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 is checking mat[i][j] == mat[i][(j + k) % n] sufficient for both left-shifted even rows and right-shifted odd rows?
1️⃣ Because any array invariant under a cyclic left shift of k steps is symmetrically invariant under a cyclic right shift of k steps
2️⃣ Because odd rows are ignored if k is an even number
3️⃣ Because the matrix is guaranteed to be a square matrix
4️⃣ Because shifting right by k is identical to shifting left by n - k only when k is zero
#LeetCode2946 #LeetCode #MatrixSimilarityAfterCyclicShifts #Java #JavaDSA #Matrix #Simulation #Array #DSA #CodingInterview #ProblemSolving #LeetCodeEasy #DailyLeetCode #JavaProgramming #CodeByTushu
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