Read the How to prepare for an interview series at my blog: http://se7so.blogspot.com/2014/01/how-to-prepare-for-interview.html

prob5.cpp

void rotate90(vector<vector<int> >& image) {
	int n = image.size();
	
	for(int i = 0; i < n; i++) {
		for(int j = 0; j < n; j++) {
			swap(image[i][j], image[n-j-1][n-i-1]);
		}
	}

	for(int i = 0; i < n/2; i++) {
		for(int j = 0; j < n; j++) {
			swap(image[i][j], image[n-i-1][j]);
		}
	}
}