Interchange the diagonal of a matrix in swift

Swift program for Interchange the diagonal of a matrix. Here mentioned other language solution.

import Foundation
/*
  Swift 4 program for
  Swap diagonal elements of matrix using recursion
*/
class Exchange
{
	// Method which are perform swap operation
	// Here x and y indicate start and end rows
	// p and q indicates start and end columns
	static func swapDiagonal(_ matrix: inout[[Int]], 
      _ x: Int, _ y: Int, _ p: Int, _ q: Int)
	{
		if (x >= y || p >= q)
		{
			return;
		}
		var temp: Int = matrix[x][p];
		// Swap the element value
		matrix[x][p] = matrix[x][q];
		matrix[x][q] = temp;
		temp = matrix[y][p];
		// Swap the element value
		matrix[y][p] = matrix[y][q];
		matrix[y][q] = temp;
		Exchange.swapDiagonal(&matrix, x + 1, y - 1, p + 1, q - 1);
	}
	// Display matrix elements
	static func showMatrix(_ matrix: [[Int]], 
      _ size: Int)
	{
		var i: Int = 0;
		// iterate rows
		while (i < size)
		{
			var j: Int = 0;
			// iterate columns
			while (j < size)
			{
				// Display element value
				print(" ",matrix[i][j], terminator: "");
				j += 1;
			}
			//  include new line
			print();
			i += 1;
		}
		// include new line
		print();
	}
	static func main()
	{
		// Define matrix element
		var matrix: [
			[Int]
		] = [
			[1, 2, 3, 4],
			[5, 6, 7, 8],
			[9, 10, 11, 12],
			[13, 14, 15, 16]
		];
		// Assume N X N matrix
		let n: Int = matrix.count;
		// Display element
		Exchange.showMatrix(matrix, n);
		// interchange request
		Exchange.swapDiagonal(&matrix, 0, n - 1, 0, n - 1);
		// Display element
		Exchange.showMatrix(matrix, n);
	}
}
Exchange.main();

Output

  1  2  3  4
  5  6  7  8
  9  10  11  12
  13  14  15  16

  4  2  3  1
  5  7  6  8
  9  11  10  12
  16  14  15  13