Section 1Understand Problem
Section 01
Understand the problem
Restate the problem precisely. Interviewers reward candidates who pause, define the contract, and name the guarantees before coding.
Problem statement
You are given an `n x n` 2D matrix representing an image. Rotate the image by 90 degrees (clockwise) *in place*. You must do the rotation without using extra space proportional to the matrix.
Example
matrix = [[1,2,3],[4,5,6],[7,8,9]] → [[7,4,1],[8,5,2],[9,6,3]]
Constraints
n == matrix.length == matrix[i].length · 1 ≤ n ≤ 20 · −1000 ≤ matrix[i][j] ≤ 1000
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