Leetcode: https://leetcode.com/problems/rotate-image/description/
Given input matrix =
[1,2,3],
[4,5,6],
[7,8,9]
rotate the input matrix in-place such that it becomes:
[7,4,1],
[8,5,2],
[9,6,3]
- (x, y), the affected point is
(y, n – x – 1), (n – x – 1, n – y – 1), (n – y – 1, x), “n” is the size of the matrix.
The rotate function=
(x, y) -> (y, n – x – 1) -> (n – x – 1, n – y – 1) -> (n – y – 1, x) -> (x, y).
- For the i th line, we start from (i, i) ( !! in for loop j = i ) , and ends at (i, n – 2 – i).
- We only need process half of them. n/2
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