Diagonal Traversal

 eg. 

1     2     3     4

5     6     7     8

9    10   11   12

13  14   15   16

Output: 1 6 11 16 2 7 12 3 8 4 

Approach:
number of diagonals = arr.length
all the diagonals are starting from i=0,
till j=arr.length that will act as right wall

package jan24_2D_Array;

public class DiagonalTraversal {
    public static void main(String[] args) {

        int[][] arr = {
                {1, 2, 3, 4},
                {5, 6, 7, 8},
                {9, 10, 11, 12},
                {13, 14, 15, 16}
        };

        /*
         Time Complexity:
         Best Case: O(n^2) – All diagonals are visited once.
         Average Case: O(n^2) – Diagonal traversal over matrix elements.
         Worst Case: O(n^2) – Covers upper half of matrix diagonals.

         Space Complexity:
         Best/Average/Worst Case: O(1) – No extra space used, in-place processing.
        */

        
        for (int diagonal = 0; diagonal < arr.length; diagonal++) {
            for (int i = 0, j = diagonal; j < arr.length; i++, j++) {
                System.out.print(arr[i][j] + "\t");
            }
        }
    }
}

Case
Time Complexity
Explanation
Space Complexity
Explanation
Best
O(n²)
All diagonals are visited once
O(1)
No extra space used
Average
O(n²)
Diagonal traversal over matrix
O(1)
In-place processing
Worst
O(n²)
Covers upper half of matrix
O(1)
No additional memory used