Codehs 8.1.5 Manipulating 2d Arrays Jun 2026

: Changing all values in a single column (e.g., grid[i][0] = 1 ).

grid[1][1] = 99; // changes center element to 99

Java 2D arrays are traversed using row-major order by default. This means your code reads or writes data across the first row from left to right, then moves down to the second row, and so on. You achieve this using nested for loops. The controls the current row. The inner loop controls the current column within that row. 2. The .length Property

By mastering the nested loop logic in 8.1.5, you are setting yourself up for success in more complex topics like 2D array traversals and the AP CS A "GridWorld" style problems. Codehs 8.1.5 Manipulating 2d Arrays

While this lesson focuses on manipulation, you often need to calculate sums to determine how to manipulate the data (e.g., "Add the row index to every value"). Tips for Success on CodeHS 8.1.5

This approach builds a string for each row, separating elements by spaces, and prints it to the console.

The grid flickered. For a terrifying second, the numbers swirled like a storm. Then—stillness. Balance. : Changing all values in a single column (e

Add a new column (each row gets an extra element):

function getEvens(matrix) let result = []; for (let i = 0; i < matrix.length; i++) let evenRow = []; for (let j = 0; j < matrix[i].length; j++) if (matrix[i][j] % 2 === 0) evenRow.push(matrix[i][j]);

Swapping values within a 2D array requires a temporary variable to prevent data from being overwritten. You achieve this using nested for loops

To manipulate a 2D array, you almost always need two loops. Think of it like a GPS: The Outer Loop: Controls the The Inner Loop: Controls the ; i < array.length; i++) { < array[i].length; // Columns // This is where the magic happens Use code with caution. Copied to clipboard 2. Common Manipulation Patterns

Ensure you are setting the value back to the array ( grid[r][c] = ... ) rather than just calculating it. 6. Pro-Tips for Success

If you are working on a specific exercise within this lesson and running into errors, I can help you debug it. Could you tell me: What is the of the exercise? What error message or unexpected output are you getting? Can you share the code snippet you have written so far? Share public link