MEDIUM NC#136 Blind #48 Math & Geometry

48. Rotate Image

šŸ“– Problem

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.

šŸ§  Visual Learning Aid

1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases

JS/TS Refreshers

  • ā€¢Array methods (`push`, `pop`, `shift`, `slice`)
  • ā€¢Object/Map/Set usage patterns
  • ā€¢Function parameter and return typing

Logical Thinking Concepts

  • ā€¢Define invariants before coding
  • ā€¢Check edge cases first (`[]`, single element, duplicates)
  • ā€¢Estimate time/space before implementation

šŸ’” Approach

  • ā†’ Transpose the matrix (swap rows and columns)
  • ā†’ Reverse each row
  • ā†’ Combined effect is 90-degree clockwise rotation
  • ā†’ Time: O(nĀ²), Space: O(1)

šŸ§­ Prerequisites

#66 Plus One

šŸ› ļø Hints & Pitfalls

Hints

  • ā€¢Transpose the matrix (swap rows and columns)
  • ā€¢Reverse each row
  • ā€¢Combined effect is 90-degree clockwise rotation

Common Pitfalls

  • ā€¢Time: O(nĀ²), Space: O(1)

šŸ§Ŗ Test Cases

Test Case 1
Not run
Input:
rotate(matrix1);
Expected:
null
Test Case 2
Not run
Input:
rotate(matrix2);
Expected:
null
Test Case 3
Not run
Input:
rotate(matrix: number[][]);
Expected:
Computed from hidden reference

šŸ“ Code Editor

šŸ“š Reference Solution

ā–¼

šŸ”— Related Problems

#50 Pow(x, n) #66 Plus One #73 Set Matrix Zeroes #149 Max Points on a Line #223 Rectangle Area
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