2D Arrays Yay!

Index Arrays

100

This code would print out the number 7 in the array:

int[][] arr = {{1,2,3}, {4,5,6}, {7,8,9}}

what is arr[2][0]?

200

This code finds the last (bottom right) value in the array nums

What is:

nums[nums.length-1][nums[0].length-1]

300

This code prints out the values on the diagonal of a square 2D array, nums

EX:

[1,2,3]

[4,5,6]

[7,8,9]

Should print out 1, 5 and 9

What is:

for(int i = 0; r < nums.length; r++){

    System.out.println(nums[i][i]);

}

400

                          !!!DAILY DOUBLE!!!                          

This code traverses through the array "bob" in reverse order (i.e. bottom right to top left)

for(r = bob.length - 1; r >=0; r--){

      for(c = bob[0].length - 1; c >= 0; c--) {

             //Some code

}

}

500

This code will find the largest value in the array named nums.

What is:

int largestNum = nums[0][0];

for(int r = 0; r < nums.length; r++){

     for(int c = 0; c < nums[0].length; c++) {

          if(nums[r][c] > largestNum) {

                 largestNum = nums[r][c];

}

}

}

System.out.println(largestNum);

Build Arrays

100

This code creates an empty 2D array of integers called nums with shape 2x3

What is int[][] arr = new int[2][3];

200

                   !!! DAILY DOUBLE !!!

This code returns the number of columns in the array nums

what is:

nums[0].length

300

This code creates an array of integers with shape 3x4 filled with random numbers from 1-10.

What is 

int[][] arr = new int[3][4];

for(int r = 0; r < arr.length; r++) {

     for(int c = 0; c < arr[0].length; c++) {

           arr[r][c] = int(Math.random()*10) + 1;

}          

}

400

This code initializes an array to keep track of 20 student names and letter grade pairs:

["Alice", "A+"]

["Bob", "B+"]

...

What is:

String[][] studentGrades = new String[20][2];

500

This code creates a new array inverse, that flips the input array nums vertically

example:

[1,2,3]                  ==>      [4,5,6]

[4,5,6]                               [1,2,3]

int[][] inverse = new int[nums.length][nums[0].length];

for(int r = 0; r < nums.length; r++){

     inverse[r] = nums[nums.length-r-1];

}

Syntax

100

This is the syntactical error in the code:

int[][] arr = int[3][4];

What is "missing the keyword new"

200

This is the syntax error in the code:

for(int r = 0; r < arr.length(); r++) {

       for(int c = 0; c < arr[0].length(); c++) {

                System.out.println(arr[r][c]);

}

}

What is "array.length() should not have parens"

300

This is the syntax error in the code:

int[][] nums = [[1,2,3], [4,5,6], [7,8,9]];

What is "square brackets are incorrect"

400

These are the TWO syntax errors with the following code:

double[] grades = new double[20][20];

for(int r = 0; r<=grades.length; r++){

     for(int c = 0; c<=grades[0].length;c++) {

            grades[r][c] = c + r;

}

}

What are missing square bracket, index out of bounds error

500

This syntax is used to make a 3D array of doubles

What is double[][][] threeD = new double[10][10][10];