Problem 1 (10 points): Short Answer

1. Two ways to subtract 1 from x are “x = x -1;” and “x--;”. What are the other two? Ans: --x; and x -= 1; _______________________________________________________________________________

2. Dangling-Else Problem. Modify the following code by inserting braces ({}) in the appropriate places to produce the output shown. Do not make any other changes apart for inserting braces.

int examGrade, quizGrade;

if (examGrade < 60)

cout << “We have a problem” << endl;

if (quizGrade < 10)

cout << “We have a real problem” << endl;

else

cout << “Ok” << endl;

If examGrade = 90 and quizGrade = 5, the following output is produced:

Ok.

Ans:

if (examGrade < 60) {
   cout << “We have a problem” <<
   if (quizGrade < 10)
      cout << “We have a real problem” << endl;
}
else
   cout << “Ok” << endl;

3. Given the following if/else statement, rewrite it as a switch statement. Assume all variables referenced in statement have been properly declared and initialized.

char result;

if (rank == JACK ||

rank == QUEEN ||

rank == KING)

result = ‘F’;

else if (rank == ACE)

result = ‘A’;

else

result = rank+‘0’;

Ans:

char result;
switch(rank) {
   case JACK:
   case QUEEN:
   case KING:
      result = 'F';
      break;
   case ACE:
      result = 'A';
      break;
   default:
      result = rank + '0';
}

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4. Identify any problems with the following line of code and discuss how you would correct them: for (int x = 0; x < 10; x--)

Ans: It is an infinate loop.

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5. Write the function header for the function letterGrade that takes a double-precision, floating point argument grade and returns a character representing the grade.

Ans:

double letterGrade(char);

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Problem 2 (10 points): What is the output of the following program?

#include <iostream>

using std::cout;

using std::endl;

void foo(int);

int main() {

cout << “a) “;

foo(6);

cout << endl;

cout << “b) “;

foo(7);

cout << endl;

cout << “c) “;

foo(8);

cout << endl;

}

void foo (int n) {

bool found = false;

for (int i = n-1; !found && i > 1; i--) {

if (n % i == 0) {

found = true;

foo(n/i);

foo(i);

}

}

if (!found)

cout << n << " ";

}

Output: (Ans)

a) 2 3

b) 7

c) 2 2 2

Problem 3 (10 points): Complete the following program. It should continually prompt the user for a volume of a sphere, and using the formula below, calculate the radius of the sphere. It will then output the results until the user enters an end-of-file character.

#include <iostream> // Necessary header file

#include<cmath>

using std::cout;

using std::endl;

int main() {

// Declare variables

const double PI = 3.14159265;

double volume;

// Prompt the user for the volume of the sphere

cout << "Enter the volume of the sphere (Ctrl-Z to quit)"

<< endl;

// Use a loop to get volumes and calculate radiuses until

// the user wants to stop

while (   cin >> volume ) {

// Calculate the radius

double radius = pow( 3 * volume / (4 * PI), 1.0/3);

// Output the result (include the volume in the result)

cout << "A sphere with a volume of " << volume

<< " has a radius of " << radius << endl;

// Again prompt the user for the volume of the sphere

cout << "Enter the volume of the sphere (Ctrl-Z to quit)" << endl;

}

}