Accessing and Updating Elements in a 2D Array

Important Tips to Remember:

•	Array indices start at 0: The first row and first column are at index 0.
•	Relative positions: Always subtract 1 to determine the correct index relative to the 1-based numbering.

Accessing Elements

To access an element in a 2D array, use the following format:

arr[row][column]

Updating Elements

To update an element in a 2D array, assign a new value using this format:

variable_name[row][column] = new_value

For example: If you want to change the value in the second row and third column, use:

array{1]{2] = new_value

Popcorn Hack:

Write code to access the scores: 92, 70, 93 and change the last score to 100

# Example 2D array representing the scores
scores = [
    [100, 85, 95, 96],  # Student0
    [98, 100, 100, 95], # Student1
    [92, 100, 98, 100], # Student2
    [100, 100, 97, 99], # Student3
    [100, 100, 100, 70],# Student4
    [100, 100, 99, 98], # Student5
    [100, 94, 100, 93]  # Student6
]

int[][] scores = {
    {100, 85, 95, 96},  // Student0
    {98, 100, 100, 95}, // Student1
    {92, 100, 98, 100}, // Student2
    {100, 100, 97, 99}, // Student3
    {100, 100, 100, 70},// Student4
    {100, 100, 99, 98}, // Student5
    {100, 94, 100, 93}  // Student6
};

System.out.println(scores[2][0]); 
System.out.println(scores[4][3]);
System.out.println(scores[6][3]);
scores[6][3] = 100;
System.out.println(scores[6][3]);

Essential points:

When accessing elements at arr[first][second], the first index is used for rows, and the second index is used for columns
Square brackets [row][col] are used to access and modify an element of a 2d array.

HW:

public static boolean isLatin(int[][] square)
{
    if(containsDuplicate(square[0]))
    {
        return false;
    }
    for(int y=0;y<square.length;y++)
    {
        if(!hasAllValues(square[0],square[y]) || containsDuplicate(square[y]) 
        || !hasAllValues(getColumn(square,y),square[y]) || containsDuplicate(hasAllValues(getColumn(square,y),square[y])))
        {
            return false;
        }
    }
    return true;
}

//frq homework on google form
int[][] grid = 
{
    {1,-2,-3},
    {-4,5,-6},
    {7,-8,9}
};

public static int[][] replaceNegatives(int[][] grid)
{
    for(int y=0;y<grid.length;y++)
    {
        for(int x=0;x<grid[y].length;x++)
        {
            if(grid[y][x] < 0)
            {
                grid[y][x] = 0;
            }
        }
    }
    return grid;
}