Q1.6

/*Given an image represented by an NxN matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees.
Can you do this in place?*/
/*
1   2   3   4          1   5   9    13          4   8   12   16
5   6   7   8          2   6   10   14          3   7   11   15
9   10  11  12    -->  3   7   11   15   -->    2   6   10   14
13  14  15  16         4   8   12   16          1   5   9    13
*/ 
/*1. Swap the element of the two side of diagonal
  2. Swap the element of the ith row and the (n-1-i)th row*/

#include <iostream>
using namespace std;

void swap(int &a, int &b) {
	int temp = a;
	a = b;
	b = temp;
} 

void transpose(int a[][4], int n) {
	for(int i=0; i<n; ++i)
		for(int j=i+1; j<n; ++j)
			swap(a[i][j], a[j][i]);
	for(int i=0; i<n/2; ++i)
		for(int j=0; j<n; ++j)
			swap(a[i][j], a[n-1-i][j]);
}

int main() {
	int a[4][4] = {
	{1, 2, 3, 4},
	{5, 6, 7, 8},
	{9,10,11,12},
	{13,14,15,16}
	};
	for(int i=0; i<4; ++i) {
		for(int j=0; j<4; ++j)
			cout << a[i][j] << " ";
		cout << endl;
	}
	cout << endl;
	transpose(a, 4);
	for(int i=0; i<4; ++i) {
		for(int j=0; j<4; ++j)
			cout << a[i][j] << " ";
		cout << endl;
	}
	return 0;
}