How do you print all elements of a matrix in diagonal order?

1. public class PrintDiagonalMatrix
2. {
3.   static final int ROW = 5;
4.   static final int COL = 4;
5.   // min of two numbers
6.   static int min(int a, int b)
7.   {
8.     return (a < b) ? a : b;
9.   }
10.   // min of three numbers
11.   static int min(int a, int b, int c)
12.   {
13.     return min(min(a, b), c);
14.   }
15.   // max of two numbers
16.   static int max(int a, int b)
17.   {
18.     return (a > b) ? a : b;
19.   }
20.   // print matrix in diagonal order
21.   static void diagonalOrder(int matrix[][])
22.   {
23.     for (int line = 1; line <= (ROW + COL - 1); line++)
24.     {
25.       int start_col = max(0, line - ROW);
26.       int count = min(line, (COL - start_col), ROW);
27.       for (int j = 0; j < count; j++)
28.         System.out.print(matrix[min(ROW, line) - j - 1][start_col + j] + " ");
29.       System.out.println();
30.     }
31.   }
32.   // print a matrix
33.   static void printMatrix(int matrix[][])
34.   {
35.     for (int i = 0; i < ROW; i++)
36.     {
37.       for (int j = 0; j < COL; j++)
38.         System.out.print(matrix[i][j] + " ");
39.       System.out.print("\n");
40.     }
41.   }
42.   public static void main(String[] args)
43.   {
44.     int M[][] =
45.     {
46.         { 1, 2, 3, 4 },
47.         { 5, 6, 7, 8 },
48.         { 9, 10, 11, 12 },
49.         { 13, 14, 15, 16 },
50.         { 17, 18, 19, 20 }, };
51.     System.out.print("Given matrix is \n");
52.     printMatrix(M);
53.     System.out.print("\nDiagonal printing of matrix is \n");
54.     diagonalOrder(M);
55.   }
56. }

Output:
Given matrix is
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
17 18 19 20

Diagonal printing of matrix is
1
5 2
9 6 3
13 10 7 4
17 14 11 8
18 15 12
19 16
20