TCPP2 Multiple Choice Exercises

Exercises 6.12 Multiple Choice Exercises

1.

What is the output of the code below?

int main() {
  int x = 0;
  int i = 1;
  while (i < 10) {
    x = i;
    i++;
  }
  cout << x;
}

0
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x is initialized to 0, but it’s value is reassigned in the while loop. Can you figure out what the final value assigned to x is?
1
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When i is 1, x is assigned the value of i, so x is 1. However, the while loop continuously increments i, so the final value of x is not 1.
9
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x is assigned the value of 9 during the last iteration of the while loop, and thus 9 is the output of the program.
10
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i is incremented to a value of 10, but since i < 10 is false, the contents of the while loop is not executed, so x is never assigned the value of 10.

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2.

What is the final value of i when the code finished running?

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int main() {
  int x = 0;
  int i = 1;
  while (i < 10) {
    x = i;
    i++;
  }
  cout << x;
}

0
🔗
i is initialized with a value of 1 and is incremented, so it will never have a value of 0.
1
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i is initialized with a value of 1 but it is incremented during the while loop.
9
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This is the final value of x when the code is finished running.
10
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In order for the while loop to terminate, the condition i < 10 must be false, and this is achieved when i is incremented to 10.

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3.

How many times does the following while loop run?

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int main() {
  int i = 6;
  while (i > 2) {
    i = i + 4;
    if (i > 8) {
      i = i - 5;
  }
}

1
🔗
Take a closer look at the while loop and conditional.
3
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Take a closer look at the while loop and conditional.
5
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Take a closer look at the while loop and conditional.
The loop will run infinitely.
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The value of i will always be greater than 2, resulting in an infinite loop.

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4.

What is the output of the code below?

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int main() {
  int j = 6;
  int i = j + 4;
  cout << "People ";
  i = i % 2;
  i = i - 1;
  while (i < 3) {
    cout << "really ";
    if (i > 0) {
      cout << "really ";
    }
    i += 2;
  }
  cout << "like Joe's Pizza." << endl;
}

People really like Joe’s Pizza.
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Take a closer look at the while loop condition.
People really really really like Joe’s Pizza.
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The code will print out three “really”s, two from evaluating the while loop condition and one from evaluating the if condition before printing out “like Joe’s Pizza”
People really really really really really like Joe’s Pizza.
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Take a closer look at the while loop condition.
The loop will run infinetly.
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Take a closer look at the while loop condition and reassignment of i

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5.

What is the output of the code below?

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int main() {
  int n = 10;
  // cout << "Da ";
  cout << "na ";
  while (n != 3) {
    cout << "na ";
    n--;
  }
  cout << "Batman!";
}

na na na na na na na na Batman!
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The code prints out eight “na”s before printing out “Batman!”
na na na na na na na Batman!
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Look over the code carefully. There are output statements before the while loop.
Da na na na na na na na na Batman!
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Will “Da” ever be printed?
It will result in an infinite loop.
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Since we repeatedly decrement n inside the while loop, it will eventually be equal to 3 and the while loop will terminate.

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6.

What is the output of the code below?

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int main() {
  int n = 10;
  cout << "Da ";
  cout << "na ";
  while (n != 3) {
    cout << "na ";
  }
  cout << "Batman!";
}

Batman!
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Take a closer look at the while loop.
Da Batman!
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Take a closer look at the while loop.
Da na na na na na na na na Batman!
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Take a closer look at the while loop.
It will result in an infinite loop.
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Since we never change the value of n, 10 will never equal 3 so the code will run forever.

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7.

What is the output of the code below?

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int main() {
  int x = 1;
  while (x < 6) {
    cout << x << "\t" << pow (x, 5) / pow (x, 3) << endl;
    x++;
  }
}

The first six perfect fifths.
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Take a closer look at the while loop and what x was initialized to.
The first six perfect squares.
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Take a closer look at the while loop and what x was initialized to.
The first five perfect squares.
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Dividing x to the power of 5 by x to the power of 3 effectively results in perfect squares.
The first five perfect cubes.
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Take a closer look at the mathematical expression inside the while loop.

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8.

Why are we allowed to use the variable x in both main and in the function definition of superSecretFunction?

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int superSecretFunction(int n) {
  int x = 0;
  return (2 + (n * n) - 5 * n / 7) * x;
}

int main() {
  int x = 1;
  cout << "After using the super secret function, we get " << superSecretFunction (x);
}

We’re using the same variable, but just reassigning the value from 0 to 1.
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We are actually using two different variables that happen to have the same name.
Although the name of both variables is x, they represent different locations in memory, and thus are different variables.
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One x is a local variable of superSecretFunction while the other is a local variable of main .
We can assign them different values but not the same value. Thus, if both were initialized to 0, then we’d get an error.
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Since they are not in the same storage location, they can store any value, including the same value.
We’re not allowed to do this. The code will result in an error.
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The code does not produce an error.

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9.

What is the output of the code below?

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int loopFive(int n) {
  while (n % 5 != 0) {
    n = n + 3;
  }
  return n;
}

int main() {
  cout << loopFive (2);
  cout << loopFive (3);
  cout << loopFive (4);
}

51510
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n is repeatedly incremented by 3 until it is divisible by 5, and this happens when n is 5, 15, and 10 for the inputs of 2, 3, and 4 respectively.
234
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Although the function returns n, n might not be its original value.
5 15 10
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Take a closer look at the output statements.
567
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Take a closer look at the while loop in the function.

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10.

The super evil villian RePete wants to annoy the city by hacking into the city’s helper robots and making them repeat everything they say 5 times. However, there’s an error in his code and now the robots won’t stop repeating! Can you find the error?

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void repeatBot(string input) {
  int n = 0;
  while (n < 5) {
    cout << input << " ";
    n--;
  }
}

int main() {
  repeatBot ("Hello, how may I help you?");
}

repeatBot can only take one word as an argument.
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A string is any number of characters or words surrounded by double quotes, not just one word.
n is declared to be 0 and 0 is always less than 5.
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The code doesn’t loop infinitely because of the value n was declared to be.
Every time the while loop runs, n is reset to 0, so it will always be less than 5.
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The initialization of n occurs outside the while loop, so the value of n does not get reset to 0.
n is declared to be 0 and we continuously decrement n so it will always be less than 5.
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Since n starts at 0 and gets smaller, the conditional for the while loop will always be true, and thus the code runs forever.

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11.

After making some changes to his code, RePete tries again. This time, however, the robots don’t repeat anything! Can you find the new error?

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void repeatBot(string input) {
  int n = 0;
  while (n > 5) {
    cout << input << " ";
    n++;
  }
}

int main() {
  repeatBot ("Hello, how may I help you?");
}

n > 5 is not a valid conditional, so the while loop doesn’t execute.
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n > 5 is a boolean statement and thus is a valid conditional.
The value of n never gets modified in the while loop.
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n is incremented in the while loop after the cout statement.
In the cout statement, only spaces are printed.
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input is also printed.
The conditional for the while loop is not met.
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Since n is declared to be 0, 0 is not greater than 5, so the while loop does not execute.

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