LeetCode Q48: Rotate Image

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

Rotate layer by layer. In each layer move 4 elements in the same time.

	class Solution {
	public:
	void rotate(vector<vector<int> >& matrix) {
	int layers=ceil(matrix.size()/2);
	int N=matrix.size();
	int n=N;
	for(int i=layers; i>=1; i--){
	int r=layers-i;
	for(int j=r; j<r+n-1; j++){
	int c=j;
	int u=matrix[r][c];
	int rt=matrix[c][N-layers+i-1];
	int d=matrix[N-layers+i-1][N-c-1];
	int l=matrix[N-c-1][layers-i];
	matrix[c][N-layers+i-1]=u;
	matrix[N-layers+i-1][N-c-1]=rt;
	matrix[N-c-1][layers-i]=d;
	matrix[r][c]=l;
	}
	n=n-2; // get to next layers inside
	}
	}
	};

view raw Q48RotateImage.cpp hosted with ❤ by GitHub