feat: add Rotate Image explanation

- Transpose + reverse algorithm approach
- Comprehensive problem analysis
- Multiple approaches and optimizations
- Edge cases and applications

Author: TechnoBlogger14o3

neetcode-150/math-geometry/rotate-image/explanation.md

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+# Rotate Image
+
+## Problem Statement
+
+You are given an `n x n` 2D `matrix` representing an image, rotate the image by 90 degrees (clockwise).
+
+You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.
+
+## Examples
+
+**Example 1:**
+```
+Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
+Output: [[7,4,1],[8,5,2],[9,6,3]]
+```
+
+## Approach
+
+### Method 1: Transpose + Reverse (Recommended)
+1. Transpose the matrix (swap rows and columns)
+2. Reverse each row
+3. Most efficient approach
+
+**Time Complexity:** O(n²) - Two passes
+**Space Complexity:** O(1) - In-place modification
+
+### Method 2: Layer by Layer Rotation
+1. Rotate matrix layer by layer
+2. Use four-way swap for each layer
+3. Less efficient than transpose approach
+
+**Time Complexity:** O(n²) - Two passes
+**Space Complexity:** O(1) - In-place modification
+
+## Algorithm
+
+```
+1. Transpose matrix: matrix[i][j] = matrix[j][i]
+2. Reverse each row: matrix[i][j] = matrix[i][n-1-j]
+```
+
+## Key Insights
+
+- **Transpose**: Swap rows and columns
+- **Reverse**: Reverse each row after transpose
+- **Local Optimum**: Efficient matrix transformation
+- **Global Optimum**: 90-degree clockwise rotation
+
+## Alternative Approaches
+
+1. **Layer by Layer**: Rotate layer by layer
+2. **Four-way Swap**: Use four-way swap for each element
+3. **Brute Force**: Create new matrix and copy
+
+## Edge Cases
+
+- Single element: Return as is
+- 2x2 matrix: Handle appropriately
+- Large matrix: Handle efficiently
+- Empty matrix: Return empty matrix
+
+## Applications
+
+- Matrix algorithms
+- Image processing
+- Algorithm design patterns
+- Interview preparation
+- System design
+
+## Optimization Opportunities
+
+- **Transpose + Reverse**: Most efficient approach
+- **Space Optimization**: O(1) space complexity
+- **Quadratic Time**: O(n²) time complexity
+- **No Extra Space**: Use only necessary space