Consider the following mergeSortHelper method, which is part of an algorithm to recursively sort an array of integers. /** Precondition: (arr.length == 0 or 0 <= from <= to <= arr.length) * arr.length == temp.length */ public static void mergeSortHelper(int[] arr, int from, int to, int[] temp) { if (from < to) { int middle = (from + to) / 2; mergeSortHelper(arr, from, middle, temp); mergeSortHelper(arr, middle + 1, to, temp); merge(arr, from, middle, to, temp); } } The merge method is used to merge two halves of an array (arr[from] through arr[middle], inclusive, and arr[middle + 1] through arr[to], inclusive) when each half has already been sorted into ascending order. For example, consider the array arr1, which contains the values {1, 3, 5, 7, 2, 4, 6, 8}. The lower half of arr1 is sorted in ascending order (elements arr1[0] through arr1[3], or {1, 3, 5, 7}), as is the upper half of arr1 (elements arr1[4] through arr1[7], or {2, 4, 6, 8}). The array will contain the values {1, 2, 3, 4, 5, 6, 7, 8} after the method call merge(arr1, 0, 3, 7, temp). The array temp is a temporary array declared in the calling program. Consider the following code segment, which appears in a method in the same class as mergeSortHelper and merge. int[] vals = {80, 50, 30, 20, 60, 70}; int[] temp = new int[vals.length]; mergeSortHelper(vals, 0, vals.length - 1, temp); Which of the following represents the arrays merged the last time the merge method is executed as a result of the code segment above?

{30, 50, 80} and {20, 60, 70} are merged to form {20, 30, 50, 60, 70, 80}.

{20, 30, 50} and {60, 70, 80} are merged to form {20, 30, 50, 60, 70, 80}.

{20, 50, 70} and {30, 60, 80} are merged to form {20, 30, 50, 60, 70, 80}.

{20, 50, 70} and {30, 60, 80} are merged to form {20, 50, 70, 30, 60, 80}.

{30, 50, 80} and {20, 60, 70} are merged to form {30, 50, 80, 20, 60, 70}.

Consider the following data field and method. Method maxHelper is intended to return the largest value among the first numVals values in an array; however, maxHelper does not work as intended. private int[] nums; // precondition: 0 < numVals <= nums.length private int maxHelper(int numVals) { Line 1: int max = maxHelper(numVals - 1); Line 2: if (max > nums[numVals - 1]) return max; else return nums[numVals - 1]; } Which of the following best describes the conditions under which maxHelper does not work as intended?

Method maxHelper never works as intended.

When the elements of nums are in nonincreasing order

When the elements of nums are in nondecreasing order

The following question refer to the following information. Consider the following data field and method. Method maxHelper is intended to return the largest value among the first numVals values in an array; however, maxHelper does not work as intended. private int[] nums; // precondition: 0 < numVals <= nums.length private int maxHelper(int numVals) { Line 1: int max = maxHelper(numVals - 1); Line 2: if (max > nums[numVals - 1]) return max; else return nums[numVals - 1]; } Which of the following corrects the method maxHelper so that it works as intended?

Insert the following statement before Line 1. if (numVals == 1 return nums[0];

Insert the following statement before Line 1. if (numVals == 0) return numVals;

Insert the following statement between Line 1 and Line 2. if (numVals == 0) return numVals;

Insert the following statement between Line 1 and Line 2. if (numVals == 1) return nums[0];

Insert the following statement between Line 1 and Line 2. if (numVals < 2) return numVals;

Consider the following method, which is intended to return the largest value in the portion of the int array data that begins at the index start and goes to the end of the array. /** Precondition: 0 <= start < data.length */ public int maximum(int[] data, int start) { if (start == data.length – 1) { return data[start]; } /* missing statement */ if (val > data[start]) { return val; } else { return data[start]; } } Which of the following can be used as a replacement for /* missing statement */ so that the maximum method works as intended?

int val = maximum(data, start + 1);

int val = maximum(data, start);

int val = maximum(data, start - 1);

int val = maximum(data[start - 1], start);

int val = maximum(data[start + 1], start);

Consider the following method. /* Precondition: 0 < numVals <= nums.length / public static int mystery(int[] nums, int v, int numVals) { int k = 0; if (v == nums[numVals - 1]) { k = 1; } if (numVals == 1) { return k; } else { return k + mystery(nums, v, numVals - 1); } } Which of the following best describes what the call mystery(numbers, val, numbers.length) does? You may assume that variables numbers and val have been declared and initialized.

Returns the number of elements in numbers that are equal to val

Returns 1 if the last element in numbers is equal to val; otherwise, returns 0

Returns the index of the last element in numbers that is equal to val

Returns the number of elements in numbers that are not equal to val

Returns the maximum number of adjacent elements that are not equal to val

Consider the following data field and method. private int[][] mat; public int mystery(int r, int c) { if (r != 0 || c != 0) { return (mat[r][c] + mystery(r - 1, c - 1)); } else { return mat[r][c]; } } Assume that mat is the 2-D array shown below. 01230 0123 1 4567 2 891011 3 12131415 What value is returned as a result of the call mystery(2, 3)?

No value is returned because mystery throws an ArrayIndexOutOfBoundsException. No value is returned because mystery throws an Array

Consider the following instance variable and method. private int[] arr; /** Precondition: arr contains no duplicates; * the elements in arr are in ascending order. * @param low an int value such that 0 < low < arr.length * @param high an int value such that low - 1 < high < arr.length * @param num an int value */ public int mystery(int low, int high, int num) { int mid = (low + high) / 2; if (low > high) { return low; } else if (arr[mid] < num) { return mystery(mid + 1, high, num); } else if (arr[mid] > num) { return mystery(low, mid − 1, num); } else // arr[mid] == num { return mid; } } What is returned by the call mystery(0, arr.length − 1, num)?

The number of elements in arr that are less than num

The number of elements in arr that are less than or equal to num

The number of elements in arr that are equal to num

The number of elements in arr that are greater than num

The index of the middle element in arr

// precondition: x >= 0 public void mystery(int x) { if ((x / 10) != 0) { mystery(x / 10); } System.out.print(x % 10); } Which of the following is printed as a result of the call mystery(123456) ?

Many digits are printed due to infinite recursion.

Consider the following method. Which of the following is printed as a result of the call mystery (1234)?

Many digits are printed due to infinite recursion.

Consider the following method. public static void mystery(int[] a, int index) { if (index < a.length) { mystery(a, index + 1); } if (index > 0) { System.out.print(a[index - 1]); } } What is printed as a result of executing the following code segment? int[] array = {6, 8, 7, 9, 5}; mystery(array, 0);

Many digits are printed because of infinite recursion.

The printRightToLeft method is intended to print the elements in the ArrayList words in reverse order. For example, if words contains ["jelly bean", "jukebox", "jewelry"], the method should produce the following output. jewelry jukebox jelly bean The method is shown below. public static void printRightToLeft(ArrayList<String> words) { if (words.size() > 0) { System.out.println(words.get(words.size() - 1)); / * missing code * / } } Which of the following can be used to replace / * missing code * / so that the printRightToLeft method works as intended?

words.remove(words.size() - 1); printRightToLeft(words);

words.remove(0); printRightToLeft(words);

words.remove(words.size()); printRightToLeft(words);

printRightToLeft(words); words.remove(0);

printRightToLeft(words); words.remove(words.size() - 1); words.remove(words.size() - 1);

Consider the following static method. private static void recur(int n) { if (n != 0) { recur(n - 2); System.out.print(n + " "); } } What numbers will be printed as a result of the call recur(7) ?

No numbers will be printed because of infinite recursion.

Many numbers will be printed because of infinite recursion.

Consider the following two methods, which are intended to return the same values when they are called with the same positive integer parameter n. public static int mystery1(int n) { if (n > 1) { return 5 + mystery1(n - 1); } else { return 1; } } public static int mystery2(int n) { int total = 0; int x = 1; while (x < n) { total += 5; x++; } return total; } Which, if any, of the following changes to mystery2 is required so that the two methods work as intended?

The variable total should be initialized to 1.

The variable x should be initialized to 0.

The condition in the while loop header should be x < n - 1.

The condition in the while loop header should be x <= n.

No change is required; the methods, as currently written, return the same values when they are called with the same positive integer parameter n.

Consider the following method. /* Precondition: j <= k */ public static void mystery(int j, int k) { System.out.println(j); if (j < k) { mystery(j + 1, k); } } Which of the following best describes the behavior of the mystery method?

It prints the integers from j to k, inclusive, in order from least to greatest.

It repeatedly prints the value j due to infinite recursion.

It prints the initial value of j a total of k times.

It prints the initial value of k a total of j times.

It prints the integers from j to k, inclusive, in order from greatest to least.

Consider the following recursive method. /** Precondition: 0 <= numVals <= nums.length */ public static int mystery(int[] nums, int v, int numVals) { if (numVals == 0) { return 0; } else if (v == nums[numVals - 1]) { return 1 + mystery(nums, v, numVals - 1); } else { return mystery(nums, v, numVals - 1); } } Which of the following best describes the value returned by the call mystery(nums, v, nums.length) ?

The number of times that v occurs in nums is returned.

The number of times that numVals occurs in nums is returned.

Nothing is returned. A runtime error occurs because of infinite recursion.

Consider the following method. public static void strChange(String str) { if (str.length() > 0) { strChange(str.substring(1)); System.out.print(str.substring(0, 1)); } } Which of the following best describes the behavior of the method?

It prints the characters of str in reverse order.

It prints the first character of str.

It prints the last character of str.

It prints the characters of str in the order they appear.

It prints nothing due to infinite recursion.

Consider the following method. public static int mystery(ArrayList<Integer> numList) { if (numList.size() == 0) { return 0; } else { int val = numList.remove(0); return val + mystery(numList); } } Which of the following best describes the value returned by the method?

It returns the sum of the elements in numList.

It returns the value of the first element in numList.

It returns the value of the last element in numList.

It returns 0 regardless of the contents of numList.

It returns nothing due to infinite recursion.

Consider the following recursive method. Assume that int val has been declared and initialized with a value that satisfies the precondition of the method. Which of the following best describes the value returned by the call what(val) ?

The number of digits in the decimal representation of val is returned.

The sum of the digits in the decimal representation of val is returned.

Nothing is returned. A run-time error occurs because of infinite recursion.

Consider the following recursive method. What is printed as a result of the call whatsItDo ("WATCH") ?

WATCH WATC WAT WA W WA WAT WATC WATCH

Unit 10 APCSA

Authored by Jeff Cougger

Computers

12th Grade

Used 5+ times

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MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Consider the following method.
public int addFun(int n)
{
if (n <= 0)
return 0;
if (n == 1)
return 2;
return addFun(n - 1) + addFun(n - 2);
}
What value is returned as a result of the call addFun(6) ?

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Consider the following method, which implements a recursive binary search.
/** Returns an index in arr where the value x appears if x appears
* in arr between arr[left] and arr[right], inclusive;
* otherwise returns -1.
* Precondition: arr is sorted in ascending order.
* left >= 0, right < arr.length, arr.length > 0
*/
public static int bSearch(int[] arr, int left, int right, int x)
{
if (right >= left)
{
int mid = (left + right) / 2;
if (arr[mid] == x)
{
return mid;
}
else if (arr[mid] > x)
{
return bSearch(arr, left, mid - 1, x);
}
else
{
return bSearch(arr, mid + 1, right, x);
}
}
return -1;
}
The following code segment appears in a method in the same class as bSearch.
int[] nums = {0, 4, 4, 5, 6, 7};
int result = bSearch(nums, 0, nums.length - 1, 4);
What is the value of result after the code segment has been executed?

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Consider the following method, which implements a recursive binary search.
/** Returns an index in myList where target appears,
* if target appears in myList between the elements at indices
* low and high, inclusive; otherwise returns -1.
* Precondition: myList is sorted in ascending order.
* low >= 0, high < myList.size(), myList.size() > 0
*/
public static int binarySearch(ArrayList<Integer> myList,
int low, int high, int target)
{
int mid = (high + low) / 2;
if (target < myList.get(mid))
{
return binarySearch(myList, low, mid - 1, target);
}
else if (target > myList.get(mid))
{
return binarySearch(myList, mid + 1, high, target);
}
else if (myList.get(mid).equals(target))
{
return mid;
}
return -1;
}
Assume that inputList is an ArrayList of Integer objects that contains the following values.
[0, 10, 30, 40, 50, 70, 70, 70, 70]
What value will be returned by the call binarySearch(inputList, 0, 8, 70) ?

-1

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Consider the following method.
public static int calcMethod(int num)
{
if (num == 0)
{
return 10;
}
return num + calcMethod(num / 2);
}
What value is returned by the method call calcMethod(16) ?

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Consider the following two static methods, where f2 is intended to be the iterative version of f1.
public static int f1(int n)
{
if (n < 0)
{
return 0;
}
else
{
return (f1(n - 1) + n * 10);
}
}
public static int f2(int n)
{
int answer = 0;
while (n > 0)
{
answer = answer + n * 10;
n--;
}
return answer;
}
The method f2 will always produce the same results as f1 under which of the following conditions?
I. n < 0
II. n = 0
III. n > 0

I only

II only

III only

II and III only

I, II, and III

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Consider the following method.
public String goAgain(String str, int index)
{
if (index >= str.length())
return str;
return str + goAgain(str.substring(index), index + 1);
}
What is printed as a result of executing the following statement?
System.out.println(goAgain("today", 1));

today

todayto

todayoday

todayodayay

todayodaydayayy

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Directions: Select the choice that best fits each statement. The following question(s) refer to the following information
Consider the following binarySearch method. The method correctly performs a binary search.
Consider the following code segment.
int [ ] values = {1, 2, 3, 4, 5, 8, 8, 8};int target = 8;
What value is returned by the call binarySearch (values, target) ?

-1

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Unit 10 APCSA

Consider the following method.public int addFun(int n){if (n <= 0)return 0;if (n == 1)return 2;return addFun(n - 1) + addFun(n - 2);}What value is returned as a result of the call addFun(6) ?

Consider the following method.public static int calcMethod(int num){if (num == 0){return 10;}return num + calcMethod(num / 2);}What value is returned by the method call calcMethod(16) ?

Consider the following method.public String goAgain(String str, int index){if (index >= str.length())return str;return str + goAgain(str.substring(index), index + 1);}What is printed as a result of executing the following statement?System.out.println(goAgain("today", 1));

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Discover more resources for Computers

Consider the following method.
public int addFun(int n)
{
if (n <= 0)
return 0;
if (n == 1)
return 2;
return addFun(n - 1) + addFun(n - 2);
}
What value is returned as a result of the call addFun(6) ?

Consider the following method.
public static int calcMethod(int num)
{
if (num == 0)
{
return 10;
}
return num + calcMethod(num / 2);
}
What value is returned by the method call calcMethod(16) ?

Consider the following method.
public String goAgain(String str, int index)
{
if (index >= str.length())
return str;
return str + goAgain(str.substring(index), index + 1);
}
What is printed as a result of executing the following statement?
System.out.println(goAgain("today", 1));