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Bhanu Bisht

Template

Matrix Patterns Template: Pattern, Code & Cheat Sheet

The Matrix Patterns pattern is one of the most frequently tested coding interview patterns. 2D array traversal, rotation, and search techniques. This template gives you a reusable code skeleton, pseudocode, and implementation in multiple languages so you can solve 8+ problems using this single mental model.

Difficulty: Medium | Time Complexity: O(m*n) | Space Complexity: O(m*n)

When to Use This Template

Use the Matrix Patterns template when you see these signals in a problem:

1.Spiral traversal — Problems asking to spiral traversal

2.Search in matrix — Problems asking to search in matrix

3.Island counting — Problems asking to island counting

Prerequisites: 2D Arrays, BFS/DFS

Problem count on W Code: 8 problems across Easy, Medium, and Hard difficulty levels.

If the problem does not match these signals, consider alternative patterns.

Pseudocode Template

function matrix_patternsSolve(input):
    // Initialize data structures
    result = initial_value
    
    // Core logic for Matrix Patterns
    for each element in input:
        process(element)
        update(result)
    
    return result

Python Implementation

python
def solve(input_data):
    """Matrix Patterns solution template."""
    result = []
    # Implement matrix patterns logic here
    for item in input_data:
        # Process each item
        result.append(item)
    return result

Java Implementation

java
public Object solve(Object[] input) {
    // Matrix Patterns template
    // Implement core logic here
    return null;
}

C++ Implementation

cpp
auto solve(vector<int>& input) {
    // Matrix Patterns template
    // Implement core logic
    return result;
}

Variations & Adaptations

The Matrix Patterns pattern has several variations you should master:

Variation 1: Spiral Traversal

This variation is useful when the problem specifically requires spiral traversal. Adapt the main template by modifying the core loop/recursion logic accordingly.

Variation 2: Diagonal Traversal

This variation is useful when the problem specifically requires diagonal traversal. Adapt the main template by modifying the core loop/recursion logic accordingly.

Variation 3: Search in Sorted Matrix

This variation is useful when the problem specifically requires search in sorted matrix. Adapt the main template by modifying the core loop/recursion logic accordingly.

Variation 4: Rotate Matrix

This variation is useful when the problem specifically requires rotate matrix. Adapt the main template by modifying the core loop/recursion logic accordingly.

Common Mistakes & Edge Cases

When implementing Matrix Patterns, watch out for:

1.Off-by-one errors — Carefully handle boundary conditions in loops

2.Missing base case — Ensure recursion terminates properly

3.Integer overflow — Use appropriate data types for large inputs

4.Empty input — Handle null/empty arrays, strings, or graphs

5.Single element — Test with minimal inputs

Edge cases to always test:

•Empty input → expected output

•Single element → correct result

•All same elements → no infinite loop

•Maximum constraints → within time limit

Step-by-Step Problem Solving Guide

1.Identify the pattern: Does the problem involve Spiral traversal, Search in matrix, Island counting?

2.Choose the template: Select the variation from above that best fits

3.Define variables: Map problem-specific entities to template variables

4.Implement the core logic: Fill in the template skeleton

5.Handle edge cases: Add boundary checks

6.Verify with examples: Trace through sample inputs

7.Analyze complexity: Confirm O(m*n) time and O(m*n) space

Frequently Asked Questions

What problems can I solve with the Matrix Patterns template?

The Matrix Patterns template applies to 8+ problems including: Spiral traversal, Search in matrix, Island counting. Look for problems that involve 2d array traversal, rotation, and search techniques..

What is the time complexity of Matrix Patterns?

The typical time complexity is O(m*n) with space complexity of O(m*n). Some variations may differ.

What should I learn before Matrix Patterns?

Prerequisites include: 2D Arrays, BFS/DFS. Make sure you are comfortable with these concepts first.

How do I recognize a Matrix Patterns problem in an interview?

Key signals: the problem involves spiral traversal; the problem involves search in matrix; the problem involves island counting. Practice identifying these cues by solving at least 10 problems using this pattern.

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