Codehs 8.1.5 Manipulating 2d Arrays 【Top-Rated ✔】

When the autograder runs, it checks for specific output patterns. Before submitting, print your array using a helper method to visualize the changes:

Imagine a spreadsheet, a chess board, or a tic-tac-toe grid. These are all perfect real-world representations of 2D arrays. While a standard array stores elements in a single row, a 2D array stores elements in and columns .

Before manipulating a 2D array, you must visualize how Java handles it. A 2D array is fundamentally an . When you declare a 2D array: int[][] grid = new int[3][4]; Use code with caution. You are creating a grid with 3 rows and 4 columns . grid.length returns the number of rows (3).

// Task 3: Write a function that swaps the first and last row function swapFirstLastRow(matrix) // Your code here Codehs 8.1.5 Manipulating 2d Arrays

public static int countTarget(int[][] arr, int target) int count = 0; for (int r = 0; r < arr.length; r++) for (int c = 0; c < arr[r].length; c++) if (arr[r][c] == target) count++; return count; Use code with caution. Algorithm B: Modifying a Specific Row or Column

int rows = nums.length; int[][] result = new int[rows][]; for (int i = 0; i < rows; i++) result[i] = new int[nums[i].length];

8.1.6 – 2D Array Challenges & Algorithms When the autograder runs, it checks for specific

: Use a nested loop to iterate through every row and column, incrementing a counter variable (e.g., totalElements ) for each value found. The Manipulation Method

If you are working through the CodeHS AP Computer Science A (Java) curriculum, you’ve likely reached and encountered Exercise 8.1.5: Manipulating 2D Arrays . This exercise is a critical step in learning how to traverse, modify, and transform two-dimensional arrays. Many students find 2D arrays tricky at first, but once you master the nested loop patterns and indexing rules, you’ll be able to solve this problem—and any future 2D array challenge—with confidence.

for(let row = 0; row < grid.length; row++) for(let col = 0; col < grid[row].length; col++) // Manipulate grid[row][col] here Use code with caution. grid.length : Gives the number of rows. While a standard array stores elements in a

If your grid is not rectangular (rows have different lengths), always use grid[r].length rather than grid[0].length for the inner loop. Conclusion

matrix[r][a] = matrix[r][b]; matrix[r][b] = matrix[r][a]; // Wrong! Original value is lost.