AP CSA - Unit 6 Arrays Test Review

Which index is the last element in an array called

nums at?

• nums.length

• nums.length - 1

Answer explanation

Since the first element in an array is at index 0 the last element is the length minus 1.

Which of the following declarations will cause a compile time error?

• int[ ] scores = null;

• int [ ] scoreArray = {50,90,85};

• String [ ] nameArray = new String [10];

• String [ ] nameArray = {5, 3, 2};

• int [ ] scores = new int [5];

Answer explanation

You can not put integers into an array of String objects

What is returned from arr[3] if arr = {6, 3, 1 , 2} ?

• 1

• 2

• 3

• 6

• 4

Answer explanation

This returns the value in arr at index 3. Remember that the first item in an array is at index 0.

What is returned from mystery when it is passed {10, 30, 30, 60}?

• 17.5

• 30.0

• 130

• 32

• 32.5

Answer explanation

This sums all the values in the array and then returns the sum divided by the number of items in the array. This is the average.

Given the following values of a and the method doubleLast what will the values of a be after you execute: doubleLast()?

• {-20, -10, 2, 8, 16, 60}

• {-20, -10, 2, 4, 8, 30}

• {-10, -5, 1, 8, 16, 60}

• {-10, -5, 1, 4, 8, 30}

Answer explanation

It loops from the middle to the end doubling each value. Since there are 6 elements it will start at index 3.

What are the values in a after multAll(3) executes?

• {1, 3, -5, -2}

• {3, 9, -15, -6}

• {2, 6, -10, -4}

• The code will never stop executing due to an infinite loop

Answer explanation

This code multiplies each value in a by the passed amt which is 3 in this case.

What are the values in a after mult(2) executes?

• {1, 3, -5, -2}

• {3, 9, -15, -6}

• {2, 6, -10, -4}

• The code will never stop executing due to an infinite loop

Answer explanation

The value of i is initialized to 0 and then never changes inside the body of the loop, so this loop will never stop. It is an infinite loop.

Which of the following statements is a valid conclusion. Assume that variable b is an array of k integers and that the following is true:

b[0] ! = b[ i ] for all i from 1 to k-1

• The value in b[0] does not occur anywhere else in the array.

• Array b is sorted

• Array b is not sorted

• Array b contains no duplicates.

• The value in b [0] is the smallest value in the array.

Answer explanation

The assertion denotes that b[0] occurs only once, regardless of the order or value of the other array values.

Consider the following code segment. Which of the following statements best describes the condition when it returns true?

• whenever the first element in a is equal to val

• Whenever a contains any element which equals val

• Whenever the last element in a is equal to val

• Whenever more than 1 element in a is equal to val

• Whenever exactly 1 element in a is equal to val

Answer explanation

Because each time through the loop temp is reset, it will only be returned as true if the last value in a is equal to val.

Consider the following data field and method findLongest. Method findLongest is intended to find the longest consecutive block of the value target occurring in the array nums; however, findLongest does not work as intended. For example given the code below the call findLongest(10) should return 3, the length of the longest consecutive block of 10s. Which of the following best describes the value actually returned by a call to findLongest?

• It is the length of the shortest consecutive block of the value target in nums

• It is the length of the array nums

• It is length of the first consecutive block of the value target in nums

• It is the number of occurrences of the value target in nums

• It is the length of the last consecutive block of the value target in nums

Answer explanation

The variable lenCount is incremented each time the current array element is the same value as the target. It is never reset so it counts the number of occurrences of the value target in nums. The method returns maxLen which is set to lenCount after the loop finishes if lenCount is greater than maxLen.