Wave Printing a two Dimensional Array

Input:

• 1 2 3
• 4 5 6

Output:

• 1 4 5 2 3 6 

package jan22;  // Package name

import java.util.Scanner;  // Importing Scanner for user input

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

        // Declare a 2D array with 2 rows and 3 columns
        // SC: O(m * n), where m = 2, n = 3
        int[][] arr = new int[2][3];

        Scanner scanner = new Scanner(System.in);  // Create Scanner object

        // Input loop to fill the 2D array
        // TC: O(m * n), each element is read once
        for (int i = 0; i < arr.length; i++) {              // O(m) loop over rows
            for (int j = 0; j < arr[0].length; j++) {       // O(n) loop over columns
                arr[i][j] = scanner.nextInt();              // O(1) input per element
            }
        }

        // Call wave traversal
        wave(arr);  // TC: O(m * n)
    }

    public static void wave(int[][] arr) {
        int column = 0;  // Start from the first column

        // Traverse each column
        // Outer loop: TC = O(n) where n is number of columns
        while (column < arr[0].length) {

            if (column % 2 == 0) {
                // Even column: top to bottom traversal
                // Inner loop: TC = O(m)
                for (int row = 0; row < arr.length; row++) {
                    System.out.print(arr[row][column] + " ");
                }
            } else {
                // Odd column: bottom to top traversal
                // Inner loop: TC = O(m)
                for (int row = arr.length - 1; row >= 0; row--) {
                    System.out.print(arr[row][column] + " ");
                }
            }

            column++;  // Move to next column
        }
    }
}


/*
Total Time Complexity: O(m * n)
- Input reading: O(m * n)
- Wave printing: O(m * n)

Total Space Complexity: O(m * n)
- 2D array of m rows and n columns
- No additional data structures used
*/

Complexity	Best Case	Average Case	Worst Case	Explanation
TC	O(m × n)	O(m × n)	O(m × n)	Each element is read and printed once
SC	O(m × n)	O(m × n)	O(m × n)	Space for storing all elements in the array

private static void method2(int[][] arr) {

    int noe = arr.length * arr[0].length;

    int col = 0;
    while (noe > 0) {

        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i][col] + " ");
            noe--;
        }

        col++;
        for (int i = arr.length - 1; i >= 0; i--) {
            System.out.print(arr[i][col] + " ");
            noe--;
        }

        col++;


    }
}