Leetcode: https://leetcode.com/problems/rotate-image/description/

Giveninput matrix= [1,2,3], [4,5,6], [7,8,9] rotate the input matrixin-placesuch 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**