GCSE AQA Computer Science Programming Languages & Integrated Development Environments (IDEs): Figure 11 shows a binary search

Question

Figure 11 shows a binary search algorithm that has been programmed in C#.

The CompareTo method is used to compare two strings. It returns:
- -1 if the first string is less than the second
- 0 if the first string is equal to the second
- 1 if the first string is greater than the second

```csharp
string[] animals = {"cat", "dog", "hippo", "llama", "ox", "rat", "tiger", "wolf"};
Console.Write("What animal would you like to find? ");
string animalToFind = Console.ReadLine();
int start = 0;
int finish = animals.Length - 1;
bool validAnimal = false;
while (validAnimal == false && start <= finish) {
    int mid = (start + finish) / 2;
    if (animals[mid] == animalToFind)
        validAnimal = true;
    else if (animalToFind.CompareTo(animals[mid]) < 0)
        finish = mid - 1;
    else
        start = mid + 1;
}
Console.WriteLine(validAnimal);
```

Complete the table below for the program in Figure 11 if the user input is wolf.

| animalToFind | validAnimal | start | finish | mid |
|---------------|-------------|-------|--------|-----|
| wolf          | False       | 0     | 7      | 3   |

You may not need to use all the rows in the table.

[4 marks]

Figure 12 shows a line of C# code that creates an array of fruit names.

```csharp
string[] fruits = {"banana", "apple", "orange", "pear", "grape", "pineapple"};
```

Extend the program in Figure 12. Your answer must be written in C#.

The program should:
- ask the user what word they would like to find
- output the message True if the word is found
- output the message False if the word is not found.

You must write your own linear search routine and not use any built-in search function available in C#.

You should use meaningful variable name(s) and C# syntax in your answer.

The answer grid below contains vertical lines to help you indent your code.

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Question 12 continues on the next page

State why a binary search cannot be used on the array fruits.

[1 mark]

Figure 13 shows an algorithm, represented using pseudo-code, that should display currency names in reverse alphabetical order, starting with yen.

There are errors in the logic of the algorithm.

- Line numbers are included but are not part of the algorithm.

```plaintext
Figure 13
dSUBROUTINE diffCurrencies(currencies)
1   currencies = ("baht", "dollar", "euro", "koruna", "lira", "rand", "rupee", "yen")
2
3   RETURN currencies[x]
4   ENDSUBROUTINE

5   FOR i ← 8 TO 0 STEP 1
6       OUTPUT(diffCurrencies(i))
7   ENDFOR
```

Rewrite line 1 and line 6 from Figure 13 to make the algorithm work as intended.

Figure 11 shows a binary search algorithm that has been programmed in C# - AQA - GCSE Computer Science - Question 12 - 2023 - Paper 1

Worked Solution & Example Answer:Figure 11 shows a binary search algorithm that has been programmed in C# - AQA - GCSE Computer Science - Question 12 - 2023 - Paper 1

Complete the table below for the program in Figure 11 if the user input is wolf.

Extend the program in Figure 12. Your answer must be written in C#.

State why a binary search cannot be used on the array fruits.

Rewrite line 1 and line 6 from Figure 13 to make the algorithm work as intended.

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