#17 Arrays, Records, Tuples and Hash Tables

2. Which of these applies to an array?

• A. Elements must be of the same data type
• B. Elements can be of any data type as there are no type rules on the array
• C. One element can contain a single value while other elements contain multiple values or data structures
• D. Specific array index values can be set to different numbers where necessary

3. In the array nums = {0,1,5,2,1), which of the following is false?

• A. There are five elements
• B. 5 is one element
• C. There are two elements
• D. Two elements have the same value

4. In the following array, which of these commands would determine the number of characters in "Crab"? zoo = ["Pig", "Wolf", "Crab"],

• A. zoo.length[3]
• B. zoo[2].length
• C. zoo[3].length
• D. zoo[3][4]

5. Which of the following would place an 'X' as the first element in a 2D array of characters which has the identifier 'grid'?

• A. grid.length(0)[0] = 'X'
• B. grid]='X'
• C. grid[0][0] = 'X'
• D. grid['X'].charAt(0)

6. Twenty-seven different coloured cubes are arranged into a larger cube shape. The colour of each individual cube is unique and is represented as a 5-bit colour code, e.g. 00000=black, 10101=pink. A 3D array of strings is used to represent the arrangement of the 27 smaller cubes into a 3x3x3 arrangement. If cube [0][0][0] represents the top-left cube on the top row, which of these represents the bottom-right cube on the bottom row?

• A. cube[0][1][2]
• B. cube[3][3][3]
• C. cube[0][3][0]
• D. cube[2][2][2]

7. Which of these is the most suitable data structure for modelling a chess board in a computerised chess game in such a way that the squares on the board store the value of the chess piece at that square?

• A. Tuple
• B. 3D array
• C. 2D array
• D. 1D array

8. When visiting all of the elements of a 2D array, which of these approaches is suitable?

• A. Use two nested iterative structures. Each time you progress to a new row, recalculate the length of that row as it may not contain the same number of columns as the row before it.
• B. Use two nested iterative structures. Each time you progress to a new row, you will not have to recalculate the length of that row as it will be the same as the row before it.
• C. Use a do-while (aka repeat-until) loop. It has built-in capabilities to handle 2D arrays efficiently.
• D. Use three nested iterative structures. The two inner iterative structures (FOR loops are commonly used) will visit each of the elements, but a third outer loop is required to manage any additional checks such as IF statements that need to be carried out.

9. A program is iterating through a 2D array, keeping track of 'rows' and 'columns' using variables called r and c. The program is seeking to add up all of the positive numbers found in the array known as 'arr' and store this in a variable called 'total', which is initialised to 0 prior to the iteration starting. Which of these is the correct syntax to be used?

• A. if(arr[r][c] < 0) { arr[c][r] = total + arr[r][c]; }
• B. if(arr[c] [r] < 0) { total = total + arr[r][c]; }
• C. if(arr[r][c] > 0) { total = total + arr[r][c]; }
• D. if(arr[c][r] > 0) { arr[c][r]= total + arr[c][r]; }

10. Which of these is true about records compared to arrays?

• A. Records are not accessed via index values whereas arrays are
• B. Arrays and records are accessed using index values but numeric indexing is more flexible in records
• C. Records are accessed using either field designators (identifiers for each field) or numeric indexes (like an array would be), depending on which is more convenient
• D. Zero-based indexing is common when arrays are used but compulsory when records are used

11. In what way is a tuple similar to an array?

• A. Its values can be changed
• B. Once it has been created it cannot grow or shrink in length
• C. It is a primitive data type
• D. Its values can all be different data types