TraversalMatrix.java

class GFG {
	static final int ROW = 5;
	static final int COL = 4;

	// A utility function to find min
	// of two integers
	static int min(int a, int b)
	{
		return (a < b) ? a : b;
	}

	// A utility function to find min
	// of three integers
	static int min(int a, int b, int c)
	{
		return min(min(a, b), c);
	}

	// A utility function to find max
	// of two integers
	static int max(int a, int b)
	{
		return (a > b) ? a : b;
	}

	// The main function that prints given
	// matrix in diagonal order
	static void diagonalOrder(int matrix[][])
	{

		// There will be ROW+COL-1 lines in the output
		for (int line = 1;
			line <= (ROW + COL - 1);
			line++) {

			// Get column index of the first
			// element in this line of output.
			// The index is 0 for first ROW
			// lines and line - ROW for remaining lines
			int start_col = max(0, line - ROW);

			// Get count of elements in this line.
			// The count of elements is equal to
			// minimum of line number, COL-start_col and ROW
			int count = min(line, (COL - start_col),
							ROW);

			// Print elements of this line
			for (int j = 0; j < count; j++)
				System.out.print(matrix[min(ROW, line)
										- j- 1][start_col + j]
								+ " ");

			// Print elements of next diagonal on next line
			System.out.println();
		}
	}

	// Utility function to print a matrix
	static void printMatrix(int matrix[][])
	{
		for (int i = 0; i < ROW; i++)
		{
			for (int j = 0; j < COL; j++)
				System.out.print(matrix[i][j] + " ");
			System.out.print("\n");
		}
	}

	// Driver code
	public static void main(String[] args)
	{
		int M[][] = {
			{ 1, 2, 3, 4 },	 { 5, 6, 7, 8 },
			{ 9, 10, 11, 12 }, { 13, 14, 15, 16 },
			{ 17, 18, 19, 20 },
		};
		System.out.print("Given matrix is \n");
		printMatrix(M);

		System.out.print(
			"\nDiagonal printing of matrix is \n");
		diagonalOrder(M);
	}
}